The German champions had two thirds of the ball during their comfortable win at the Etihad Stadium.
The City manager told Sky Sports News: "I think that we played very badly. I think that Bayern Munich played a very good game, they always play very well.
"Not enough possession of the ball. We didn't have enough time with the ball in our field. That was the worst thing. I think that we were playing in a very different way. I think that they that had possession of the ball.
"All of the games are important in the group. I think that we must revise a lot of things before we play against Everton at the weekend, as that game is important also."
The result leaves City second in their group.