Heisey homered to left field in the first inning and doubled down the left-field line in the third. The Reds' fourth outfielder is 10-for-18 in his past seven games and is hitting .588 in his most recent six starts.
"Kind of the name of the game is those big two-out RBIs, especially on the offensive side," said Heisey, who has five home runs this spring. "Defense, it's trying to eliminate those and getting a big out when you need it. Hopefully come the season time, we can be one of the best teams at getting those two-out RBIs when we need them late in games or when we're trying to tack on runs."
Neftali Soto was 4-for-4 with a home run and three RBIs, and Todd Frazier and Kristopher Negron each had two hits.
The Reds, who hit four home runs, did much of their damage against Brewers right-hander Tyler Thornburg, who is battling for a roster spot as either a starter or reliever.
Thornburg gave up seven runs on seven hits in 2 2/3 innings. Just four of the runs were earned, as the Brewers committed two errors behind Thornburg, including one immediately preceding Heisey's homer.
Brewers reliever Francisco Rodriguez made his first appearance of the spring and gave up Soto's two-out solo homer. Rodriguez missed the first two weeks of camp because of an issue with his work visa, and he was delayed further after he stepped on a cactus earlier this week.
"I can definitely feel it right now," Rodriguez said after limping to his locker in the clubhouse. "In my career I learned the difference between injury, pain and soreness. This is not an injury, so I have to go through it."
Ryan Braun and Aramis Ramirez each had two hits, and Mark Reynolds knocked in two runs off Cincinnati closer Aroldis Chapman in the fourth. The game marked the first time Ramirez had played two consecutive days this spring, and he had an RBI double among his hits Saturday.
Up next for Reds: Billy Hamilton has a .400 on-base percentage with eight hits and six walks this spring, which has helped him nab seven steals. Hamilton is expected to play Sunday when the Reds host the A's at 4:05 p.m. ET at Goodyear Ballpark on Gameday Audio. Tony Cingrani is scheduled to start opposite Oakland's Sonny Gray.
Chris Gabel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.