Eighteen-year-old Austrian left-back Marco Friedl - promoted to the first team earlier this summer - and youth players Franck Evina (2) Marco Hingerl (2), Raphael Obermair and Michael Strein were also on target in Herzogenaurach. Mario Foth grabbed Bruck's only goal.
Bayern are now two from two in summer friendlies, following their 4-1 win against Wolfratshausen earlier in the week.
Carlo Ancelotti's troupe are next in action in Saturday's Telekom Cup, before heading to China and Singapore as part of the Bundesliga World Tour (16-28 July).
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