The best way to do this is to make a new save as Bayern Munich and go in the PES League in Division 2 also make the difficulty beginner you will win games (even simulated ones) easier.
Simulate the entire first season, this will allow your players to become better than they already are (Ribery and Lahm both became 95+ for me).
Now simulate your entire second season again, your players will become even better. You're team is better than everyone else in the league so you will win the league and get into Champions League.
Okay you are now on the third season, like with season 2 you are better than everyone else so the odds are you will win the League and Cup so you can just sim the games. You will want to simulate every game and only play the Champions League games (You can simulate them if you want to, I did. But if you want to be on the safe side play them)
At the end of the season you will unlock the achievement.
It will only take 2 hours at most.
Doing it this way also unlocks you 2-3 other achievements