Nottingham Forest had no answer to an in-form Erling Haaland at the Etihad, with the Norwegian striker bagging his second hat-trick inside a week for the champions.
Julian Alvarez added a brace for the home side who could even afford to leave Kevin De Bruyne on the bench until the 69th minute.
It was a sobering evening for Forest whose best chance of the game fell to Renan Lodi who should have hit the target with a header with the scoreline at 1-0.
