What makes a flask worth your money is its ability to slow down heat transfer – either in or out – via a layer of almost airless space sandwiched between the flask’s inner and outer walls. Depending on their size and performance, the best flasks can keep drinks hot or cold for hours, sometimes an entire day, and sometimes even longer.
There are 1l giants with integrated cups, which hold at least several cups of tea to last a cold hiking trip, and mid-sized yet compact vessels for hiking. Then there are coffee-cup-sized flasks to slip in your bag for the morning commute. Some flasks are better suited to drinking cold drinks from, owing to the open design of their mouthpiece.
In my tests, I considered quality, heat retention and price. The Thermos stainless steel king flask came out on top, but the Black & Blum explorer flask duo is great for families and couples with its two integrated cups. For smaller drinks on the go, I’d recommend the Contigo luxe autoseal travel mug, which has a neat one-handed operation. Keep reading for the rest of my top picks.
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The best flasks for 2026 are:
- Best overall – Thermos stainless steel king flask: £28.60, Amazon.co.uk
- Best budget option – Dunelm hot drinks flask stainless steel: £5, Dunelm.com
- Best with two cups – Black & Blum explorer flask duo: £49.95, Amazon.co.uk
- Best mid-to-large flask – Hydroflask 828 ml hot flask and cup: Was £44.95, now £35.09, Amazon.co.uk
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Thermos stainless steel king flask
Rating: 5/5
Best: flask overall
Material: 18/8 food grade stainless steel
Weight: 650g
Capacity: 1,200ml
Max temperature preservation times: Hot for 24 hours, cold for 24 hours
Dishwasher safe: Yes
Why we love it
- Twist and pour stopper
- Collapsible handle
- Cup included
Take note
- The cup can get hot in your hands
As Thermos has become synonymous with insulated flasks, naturally, the supersize “steel king” was going to be pretty hard to beat. It has a whopping 1.2l capacity, and I was genuinely quite stunned by how hot it kept my water for more than 24 hours. Most of the ice in my cold drink was still solid after 24 hours, too – you could fill your Thermos in the morning and it will still be refreshingly cool the following day.
It’s sturdy but surprisingly lightweight for its size, and the handle, which is collapsible (to save on space), helps with one-handed carrying and pouring. Everything about the flask feels exceptionally well-made – from the thick-rimmed stainless steel cup (which doesn’t have a handle but is still nicely capacious) to the twist-and-pour stopper. My one quibble would be that the stainless steel cup can feel hot in your hands when the liquid inside is especially scorching. However, never having to completely remove the screw cap before pouring will make for smoother al fresco pit stops. A classic for a reason. I can’t knock it.
Buy now £28.6, Amazon.co.uk
Dunelm hot drinks flask stainless steel
Rating: 4/5
Best: budget flask
Why we love it
- Compact and lightweight
Take note
- Hand-wash only
- Very small cup
Don’t let the price of Dunelm’s hot drinks flask give you concerns about its performance. While Dunelm hasn’t actually stated how long its flask keeps drinks hot or cold for, I tried testing hot water around the 12-hour mark, which felt a fair test taking into consideration its smaller size (500ml), and it was still hot. For just £5, I was impressed.
It’s also the perfect flask for solo hikers as it’s not too bulky and feels incredibly light when empty, and it has one little integrated cup as the lid. The lid is tiny – more espresso rather than cuppa-sized, but it’s worth it when factoring in space-saving.
Key specifications
Buy now £5, Dunelm.com
Black & Blum explorer flask duo
Rating: 4.5/5
Best: flask with two cups
Why we love it
- Perfect for couples
Take note
- A little bulky
Black & Blum’s explorer flask duo is built for outdoor adventures for two, with its large 1l capacity and two integrated cups, one attached to each end. It’s a nice touch that they’re also double-walled, which helps keep drinks hot for longer, particularly as the cups are wide and flat, which would, in theory, allow more heat to escape. To compare, I tested the heat retention of the Hydroflask cup and these ones side by side, and they were fairly on par.
The brand claims it keeps drinks hot for 24 hours and, when checking on hot water at the 24-hour mark, it was piping hot, and I’m sure it could have stayed hot far longer.
It is quite heavy and bulky, and there isn’t a rubber base, so it’s a little clunky and noisy to place down. But it seems built to last, with a solid stainless steel structure and a reassuringly thick nylon strap, which, in contrast to, for instance, the harder handle on the Hydroflask, was more comfortable to hold.
Key specifications
Buy now £49.95, Amazon.co.uk
Circular&Co reusable water bottle
Rating: 4/5
Best: flask for ease
Why we love it
- Recycled and recyclable
- Compact
- Comfortable carry loop
- Quick access with the click-down lid
Take note
- Minor, temporary drip issue with click-down lid
Circular&Co is dedicated to sustainable drinkware. I’m a big fan of its coffee cups made from recycled takeaway cups, and its water bottles also put waste to good use, being made of 90 per cent recycled stainless steel. The brand says it recycles the bottle properly if you send it back at the end of its life, but you can also put the base in household metal recycling and lids into household plastic recycling. Just make sure the two seals and carry strap are removed first.
More for glugging than sipping, this bottle makes much more sense as a cold-water bottle than one for hot drinks. I filled it with ice and when I checked on it after two days, it had only partly melted, so that really impressed me. Hot water was hot but not piping hot after 12 hours. Remember to close the click-down lid when you’re not drinking from it – I didn’t, and it does make a difference.
The bottle has a slim shape that slots conveniently into a bag and has a minimalist monochrome design with understated branding towards the base. I like the comfort of the flexible carry loop, and there’s a rubber base so it doesn’t make a loud clang when set down on the table.
It couldn’t be quicker or easier to take a sip, as there’s a press-to-close lid, but I did find that one singular drop would escape if I drank from the lid, clicked it closed and then immediately flipped the bottle to test for leakage. Otherwise, the bottle proved completely leakproof, so I wouldn't worry about putting it in a bag.
Key specifications
Buy now £33, Amazon.co.uk
Hydroflask 828ml hot flask and cup
Rating: 5/5
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Best: mid-to-large sized flask
Why we love it
- Incredible heat retention
- Large integrated cup
- Easy to clean
Take note
- Matte black design looks less premium than stainless steel
The Hydroflask 28oz (828ml) hot flask and cup was one of the top performers when it came to sheer heat retention. It claims to keep drinks hot for 30 hours – after testing hot water at the 30-hour mark, it was so hot it was still steaming. This might be partly due to the design of the rubber stopper, which extends further down inside the flask than others. The flask also has one large integrated cup, which is deep enough to give a home comfort feel.
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Shaking the flask upside down didn’t cause any leaks, and the pour is nice and clean. The matte looks less premium than a shiny finish, but it still looks smart and I can’t see any scratches on it yet. It’s dishwasher-safe, making it easy to clean, and it has a carry loop and a handle for easy pouring.
Key specifications
Buy now £35.09, Amazon.co.uk
Chilly’s stainless steel series 3 flip bottle
Rating: 4/5
Best: designed flask
Why we love it
- Fun design and colours
- Rubber base
Take note
- Not everyone will like the nozzle mouthpiece
- Straw doesn’t reach the very bottom of the bottle
The Chilly’s stainless steel slip bottle is the best-looking insulated water bottle I’ve owned. It comes with a stainless steel body, but you can also choose a colour, including olive green and pastel pink. More importantly, it lived up to its claims of keeping drinks cold for a whopping 75 hours in my tests.
The antimicrobial nozzle has a straw connected to it that extends down into the bottle, making this definitely a bottle suited to drinking cold drinks rather than hot. The straw isn’t actually long enough to reach the dregs at the bottom of the bottle, and it seemed to take a little more effort to suck up the drink. This might not have been as marked with a smaller bottle, though.
It’s designed to be fully leak-proof and lives up to its claim, with no spills or drips or dribbles. The 90 per cent recycled stainless steel body looks great and while the bottle on the whole feels sturdy and made to last, I did notice a few scratches not long after I started using it. It’s also a bit annoying to clean, as it’s not dishwasher-safe and you need to clean the inside of the straw, though Chilly’s includes a small cleaning brush specifically designed for this. It also has a convenient carry-loop.
Key specifications
Buy now £48, Chillys.com
Lifeventure TiV vacuum flask
Rating: 4.5/5
Best: rugged budget flask
Why we love it
- Slim and very portable
- Brilliant temperature retention
Take note
- The cup is fairly small
This 700ml flask boasts all the perks of a larger option while stripping away the extra bulk. With a copper coating to improve heat preservation, it boasts the ability to keep drinks hot for up to eight hours. Impressively, I found mine was still nice and warm after around 20 hours, which is pretty good going. Equally impressive was the flask’s ability to keep drinks chilled – there were still ice cubes in my cold water after 24 hours.
Should you prefer sipping hot tea and coffee from a cup rather than straight from the flask, this is a brilliant, compact choice. Unscrew the flask’s lid and it becomes a cup, although, admittedly, quite a small one, so you will probably need to fill it a few times to quench your thirst.
The flask isn’t dishwasher safe, but this is a minor annoyance with an otherwise very efficient and purse-friendly piece of kit.
Key specifications
Buy now £22.99, Lifeventure.com
Ocean Bottle flask
Rating: 5/5
Best: environmentally conscientious flask
Why we love it
- Conscientious choice
- Versatile mouthpiece
- Carry loop for portability
Take note
- The mouthpiece can drip momentarily after the lid is removed
A conscientious choice when it comes to the materials used and environmental impact, this insulated flask from Ocean Bottle is largely made up of recycled stainless steel and ocean-bound plastic. On top of this, the brand says buying one bottle will fund efforts to prevent the equivalent of 1,000 plastic bottles from ending up in the ocean as plastic waste – so you can feel genuinely good about buying this one.
Water, coffee and even thicker smoothies and soups aren’t off limits, thanks to the bottle-esque mouthpiece. Easy to grab, owing to the flexible carry loop, you can unscrew the larger lid for cleaning and chucking in ice. My drinks were still impressively hot after six hours and refreshingly chilled after the same amount of time – cold enough that some of the ice I dropped in there was still intact. However, after using this bottle a fair bit, I’ve noticed that water collects between the lid and the mouthpiece so that when I unscrew the lid, it drips quite a bit. I thought this could be because I’d put it through the dishwasher when I shouldn’t have, but I checked, and the brand does actually state it’s dishwasher safe. This might be a one-off issue with the bottle I tested, or an issue through wear and tear, but it’s worth keeping in mind.
Key specifications
Buy now £35, Amazon.co.uk
Contigo luxe autoseal travel mug
Rating: 4.5/5
Best: small flask for ease
Why we love it
- The mouthpiece is convenient
- It’s small and compact
There’s something satisfyingly simple about this travel mug from Contigo. Press the large button on the lid, and your beverage will flow from a hole in the lid. As the flow of liquid is more concentrated than it is from larger mouthpieces, it feels almost similar to a mini vortex, which is fun. My water was hot after five hours, and cold after 12.
Drinking from this flask is a one-handed operation, as you don’t need to unscrew the lid before taking a sip. The lock on the lid will also prevent the button from being pressed when you don’t want it to be – say, when it’s being pushed up against your laptop in your bag. The flask is also very compact, narrow (making it easy to hold in one hand) and lightweight to carry. It’s a sleek bit of kit when it comes to design as well, with its all-over metallic finish, although there’s a range of other colours to choose from, too.
Key specifications
Buy now £39.09, Amazon.co.uk
Thermos superlight drinks flask
Rating: 5/5
Best: lightweight flask
Why we love it
- Looks great
- Light and compact
Take note
- Not everyone will like the mouthpiece for hot drinks
There’s so much to like about this little flask from Thermos. On first impressions, it has a sleek, simple look to it – it’s slim, compact, and the lightest of all of the flasks I tried, making it ideal for taking it with you on the go.
There’s a little button that releases the lid, so opening the flask is a breeze, and the mouthpiece is one of the best (if not the best) I've tried – wide and curved, for effortless, comfortable sipping.
When it came to the temperature test, my water was still chilled after a full 24 hours, as promised. Meanwhile, coffees and teas were still piping hot after 10 hours, so rest assured, this flask will keep drinks toasty until the commute home.
Key specifications
Buy now £22, Amazon.co.uk
Larq bottle purevis
Rating: 4.5/5
Best: high-tech flask
Why we love it
- Self-cleaning technology
- Stylish design
Take note
- Pricey
- Not recommended for tea and coffee
If you feel uneasy about water quality while travelling, Larq’s self-cleaning water bottle is a high-tech investment that has blazed a trail with its patented UV-C light hidden in the lid, eliminating nearly all (99.9 per cent) of bio-contaminants inside.
Looking a little sci-fi, the flask has a button on the lid, which can be pressed for either a short (one-minute) UV-C cycle, or you can choose adventure mode (three minutes) for extra peace of mind. Beneath the intimidating tech, though, the purevis is also just an excellent flask – my water remained hot after 12 hours, and there were still cubes of ice in my cold water after 24 hours. Importantly, please note that purification will be less effective with ice in the bottle, as this may partially block the UV-C light.
A clean bottle should help to keep that musty bottle smell at bay, and, while I admit I may have been swayed by the knowledge my water was completely clean, I did find my water tasted fresher for being purified. I liked that the bottle will clean itself automatically every two hours and, unlike the rest of my tech, only needs to be charged every month or so. It is worth noting that the brand doesn’t recommend using the bottle for drinks such as coffee and tea.
Key specifications
Buy now £89, Livelarq.com
Partner in Wine wine bottle
Rating: 4.5/5
Best: flask for wine
Why we love it
- Lightweight
- Good choice of colourways
Take note
- The mouth of the lid is too narrow fo ice cubes
As photogenic as they come, this insulated flask from Partner In Wine has been purpose-built for keeping your bottle of plonk cool for up to 24 hours. A great purchase if you really resent sipping on ever-so-slightly warm wine during the summer months, this would be perfect for filling up before picnics, festivals and any al-fresco gatherings when you would rather leave the wine cooler at home. It will fit one bottle of wine perfectly, and feels markedly lightweight for a bottle of this size (750ml).
While I wasn’t able to test this flask during the summer months, I still found that fridge-chilled wine stayed suitably cold for 24 hours. There’s no chance of vino spillages, either, as I can attest that the lid, which screws on easily and securely, is leak-proof. If you like ice in your wine, it’s worth noting the mouth of the bottle is quite narrow (indeed, wine-bottle narrow), so typical ice cubes won’t fit through.
While the black colour I tested is currently sold out, there are plenty of other dreamy hues to choose from, including soft pastels and all-over stainless steel.
Key specifications
Buy now £40, Partnerinwine.co.uk
Hydro Flask coffee mug
Rating: 4/5
Best: insulated mug
Why we love it
- Versatile lid and mouthpiece
Take note
- Not leak-proof
Sometimes, it just feels better to drink from an actual mug than a flask – particularly when you’re not actually heading into the wild, but sitting at your desk, wanting your tea or coffee to stay hot for a few hours longer.
This insulated mug isn’t leak-proof, so you won’t be carrying it around in your bag, but if you tend to forget about your cups of tea until they’ve turned tepid, it’s ideal. The matte finish is nice in the hand, and while the brand doesn’t specify for how long it should keep drinks hot or cold, my boiled water was still fairly hot after four hours, which is all you really need for a tumbler like this.
When it came to ease of use, the lid can be placed on at any angle, and the mouthpiece slides open and close easily. The mouthpiece can also be removed completely, if you’d prefer to drink straight from the mug.
Key specifications
Buy now £28.95, Amazon.co.uk
Stanley quencher H2.0 flowstate tumbler
Rating: 4/5
Best: tumbler
Why we love it
- Ergonomic handle
- Fits into some car cup-holders
Take note
- Not leak-proof
- It’s heavy
An unlikely product to have taken TikTok by storm, Stanley’s quencher flowstate can barely stay in stock. But is it worth the (considerable) splurge? Boasting a 1.2l capacity, the reusable tumbler keeps cold drinks chilled for up to 11 hours (or two days when iced). I tested these claims with an ice-cold smoothie, which stayed deliciously chilled. The ergonomic handle adds to its ease of use, while the narrow base that fits some (but not all) car cup-holders is a nice touch.
Though it’s easy to switch between the three lid positions, the full-cover top failed to pass the leak-proof test. This completely rules out the quencher in terms of carrying it loose in a bag, which is quite a big drawback, considering the price. There’s also no denying it’s heavy, and the sheer size of the thing is slightly impractical for lugging around a city during the commute. But when working from home, I appreciated the large capacity, as it helped boost my water intake (the colours are pretty, too).
Key specifications:
Buy now £45, Stanley1913.co.uk
Thermos ultimate insulation flask
Rating: 4/5
Best: flask for commuting
Why we love it
- Sturdy design
- Lightweight
This is a really solid little Thermos that does pretty much everything you’d ask of a flask. Thermos claims the flask retains temperatures for 24 hours, and it certainly did keep water cold and coffee warm over the full period. I was particularly impressed by how secure the flask felt, and I had no concerns about it leaking while bouncing around in my work bag on the Tube, in the car, or even while cycling, so it’s ideal for commuting.
The silicone rings make the flask feel extra sturdy, which I appreciated when out hiking, but, for most outdoor adventures, I’d probably opt for a flask that has a greater volume. That being said, it’s lightweight and has a decent 500ml capacity, which feels just right for taking tea or coffee into the office.
Key specifications
Buy now £43.77, Amazon.co.uk
Your questions about flasks answered
What is the best flask?
If you’re looking for a large flask, the Thermos stainless steel king flask is excellent when it comes to temperature regulation and overall quality of design. It’s a pleasure to use, and it feels built to last for years. Also 1l, the Black & Blum explorer flask duo has two cups instead of one, which gives it an edge if you’re sharing between two. The Hydroflask 828 ml hot flask and cup is a little smaller and more compact and boasts stunning heat retention of up to 30 hours, so it’s another seriously strong option.
How I tested travel flasks
Why you can trust IndyBest reviews
Lois Borny has been part of the IndyBest team since 2021. She has written about household essentials (such as vacuum cleaners), fashion, and a whole lot more in between. When testing items, Lois factors in quality, value for money, and, ultimately, whether the products are effective and fit for purpose. Every flask on her list has been put to the test under real-world conditions. If she doesn’t think a product is worth buying, it won't make the cut.
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