All of Alonso's home runs have come in the last nine games he's played.
Milwaukee shortstop Donnie Murphy had a home run, his second of spring, and a double. Murphy, who came into the game with three spring RBIs, knocked in three runs.
The Brewers' leadoff hitter and right fielder, Norichika Aoki, and third baseman Blake Davis each had doubles.
Milwaukee pitcher Wily Peralta allowed six runs on 10 hits in 5 1/3 innings with three walks and four strikeouts. Peralta is projected to be the No. 3 starter in the Brewers' rotation.
San Diego starting pitcher Eric Stults, slated to be the No. 4 starter in the rotation, allowed four runs on seven hits with four strikeouts.
"Stults was Stults today. I thought the mix of pitches was what Eric does," said Padres manager Bud Black. "I thought the curveball was as good as we've seen all spring. He had good rotation, good spin and I thought the fastball at the top of the zone was good, too."
Mark Kotsay reached base three times and Cody Ransom hit a home run, his fourth, to pace the Padres' offense. Jedd Gyorko added two hits as well.
Up next: Jason Marquis, the projected No. 3 starter in the Padres' rotation, gets the start at 1:05 p.m. PT on Monday against the Rangers at the Peoria Sports Complex. Marquis is set to throw six or seven innings in his final Cactus League start. He's added a changeup to his repertoire this spring, with good results. He has a 2.25 ERA in four appearances.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.