Breno tweeted at the weekend complaining about being forced to train and play for Bayern's reserves while the top team played a friendly.
''He's apologized to the team and the coach and he's been training well,'' Bayern chairman Karl-Heinz Rummenigge said Tuesday. ''Now he should stop tweeting and concentrate on football.''
Rummenigge said Breno had been given a ''pale yellow'' card but that ''nothing else'' should happen again.
Bayern coach Jupp Heynckes said he sent Breno to the reserve team because he needs playing time.
Breno is under an arson investigation and the club has stood behind him.
Munich prosecutors are investigating whether Breno set fire to his rented villa in September at a time when he was reportedly going through personal problems.
He was arrested but was released with Bayern's help. The club also obtained permission from Munich authorities for Breno to travel with the club to Qatar for a midseason training camp this month.
Breno arrived in Munich in 2008 as a promising defender but has had to overcome several injuries and hasn't played much for the Bundesliga powerhouse.
Bayern can avenge its loss to Borussia Moenchengladbach in the season opener when it kicks off the second half of the Bundesliga season against the same opponent on Friday.