Bruce, who was hitting .162 coming in, scored twice and singled during a five-run sixth inning.
Michael Lorenzen helped his cause in a bid for the Reds' final rotation spot by allowing four hits and one run over four innings against the Brewers' opening-day lineup.
Reds closer Aroldis Chapman left the game after pitching to one batter in the fifth inning for precautionary reasons. There were initial concerns about his right hamstring, but Chapman said there was no injury. It may have been more of a miscommunication, Reds manager Bryan Price said.
"We went out to check on him and the word 'hamstring' came up and with his history, we were being extra cautious," Price said. "It may be a non-issue and no more than a miscommunication. But at this point in time, there was way to take a chance there. I don't think there is anything to worry about."
Ryan Braun had an RBI single in the first inning for the Brewers. Adam Lind and Khris Davis had RBI singles in the sixth.
Mike Fiers, who will be the No. 5 starter for Milwaukee, allowed only three hits over five innings but walked four.
Reds: Lorenzen's ERA for the spring is 1.80 and he handled Milwaukee's everyday lineup well.
"It was a fun, competitive environment. They got on me early and we started mixing it up a little bit," he said. "I threw a 3-2 changeup to strike out Braun that was huge. That let (catcher Brayan) Pena know 'I can trust his changeup and his slider' and we started mixing up a little more. It made me feel a lot better about myself and where I'm at to compete at this level."
Brewers: Fiers will stay behind and get one more start in a minor league game here on Sunday. He wants the extra work after missing a turn with a minor shoulder setback two weeks ago.
"For me, it's good to get back out there to face more hitters and work on my stuff again," he said. "I don't think I'm 100 percent ready, so I'll take one more before the real one. I felt good today but I'll take another one."
GREGG MAKES THE REDS
The Reds informed RHP Kevin Gregg that he has made team as a non-roster invite. The 36-year-old Gregg, who allowed two earned runs in seven appearances in Cactus League play, struck out six and did not allow a batter.
"We feel it's better for both of them to go out, get regular at-bats and be ready in case something did happen over the long haul," Melvin said. "The bench is going to be more defense oriented. Our bats are in the lineup."
Milwaukee also sent C Nevan Ashley, OF Matt Long and RHP Ariel Pena to their minor league camp for reassignment.
Brewers: RHP Kyle Lohse, the opening-day starter, will make his final spring tuneup against the Chicago Cubs in Mesa.