Bruce smacked a pitch from Marco Estrada (2-6) into the right field stands to break a 4-4 tie, finishing the game 3-for-4. The Reds sent 10 men to the plate in the big frame to win going away.
Ramon Hernandez added a two-run shot and an RBI single, and Joey Votto stroked a run-scoring single among his three hits as Cincinnati rebounded after two straight losses to the Brewers.
Bill Bray (2-1) earned the win with a scoreless bottom of the ninth inning.
Yuniesky Betancourt had an RBI single for Milwaukee.
Brewers starter Shawn Marcum lasted six innings, yielding three runs on six hits.
Celebrity Families of 2014 [PHOTOS]