Miyata, a race winner in both SUPER GT and Super Formula, will accompany the Toyota World Endurance Championship squad for the remaining rounds of the season that don't clash with his existing commitments in Japan, starting with the Le Mans 24 Hours next month.
The 23-year-old will also be involved in development work at Toyota Gazoo Racing Europe's Cologne base.
Toyota's statement revealed that Miyata already participated in a simulator session at TGR-E last year and "impressed the team with his driving performance, and set competitive lap times, to earn his selection as a WEC Challenge driver".
It added that Miyata's "continued participation in the programme will be decided based on performances and development progress".
Miyata, who has been vocal about wanting to race overseas in the future, currently represents leading Toyota squad TOM'S in both SUPER GT's top GT500 class and Super Formula.
He stepped up to Super Formula full-time in 2021 after winning the previous year's Super Formula Lights title, and secured his first victory in the single-seater series at Suzuka last month.
In SUPER GT, he scored a first GT500 win alongside Sacha Fenestraz last year at Fuji Speedway, and added a second triumph alongside new partner Sho Tsuboi at the same track earlier this month.
The Toyota WEC Challenge programme has been dormant since Kenta Yamashita was chosen to race in the LMP2 class for High Class Racing during the 2019-20 season.
Yamashita opted to quit the WEC and focus on his Japanese racing commitments on the conclusion of that campaign.
That opened the door for Ryo Hirakawa to take his place on Toyota's roster of test drivers and eventually step up to replace the retiring Kazuki Nakajima as a race driver for the start of the 2022 WEC campaign.
Toyota's statement made no mention of any on-track opportunities for Miyata. A clash between the final round of SUPER GT at Motegi and the WEC's Bahrain weekend rules out an appearance in the traditional end-of-season rookie test.
In addition, it was announced that two Toyota-backed Japanese Formula 4 drivers, Jin Nakamura and Rikuto Kobayashi, will participate in a training session at the Le Mans 24 Hours that will allow them to "experience first-hand how WEC drivers and engineers take on the challenge of Le Mans".
