The Cubs took a four-run lead into the seventh inning, but the Brewers posted a five-spot on RBI hits from Logan Schafer, Pete Orr and Nick Ramirez.
Trailing 7-6, the Cubs loaded the bases in the seventh and went ahead on pinch-hitter Brett Jackson's two-run single. Another run scored on an error by third baseman Orr and a sacrifice fly by Casper Wells.
Kyle Hendricks, the Cubs' Minor League Pitcher of the Year in 2013, gave up two runs on three hits and two walks over three innings in his second Cactus League start.
"I'm much happier with this [start]," Hendricks said. "I'm just disappointed that we go out and score two runs and then I go out and give them both back up. That will all work itself out as I get out there more and am more consistent with my mechanics."
Matt Szczur singled to lead off the bottom of the first and scored two outs later on Ruggiano's second home run of the spring, connecting off Tyler Thornburg, who was making his first spring start and third appearance. The Brewers tied the game in the second on an RBI double by Jeff Bianchi and sacrifice fly by Martin Maldonado.
Cubs right fielder Ryan Sweeney had to leave the game after chasing Bianchi's double because of soreness in his right knee. Sweeney was listed as day to day.
Javier Baez, the Cubs' top prospect, greeted Zach Duke with a double to open the fifth and then scored on Lake's single to put Chicago ahead, 3-2.
Hiram Burgos walked Luis Valbuena to start the sixth, and he scored on Rizzo's triple. Ruggiano followed with an RBI single.
Milwaukee's Ryan Braun was greeted by a chorus of boos from the sellout crowd during his two at-bats. Hendricks struck Braun out to end the first, but the Brewers outfielder doubled in the third.
"He got me on the second at-bat, but that wasn't a bad pitch," Hendricks said. "His barrel stays through the zone very well. I could've thrown a different pitch to him -- but it was a good pitch, and he's a really good hitter. He's going to get his hits."
Did Hendricks hear the crowd?
"You could hear those boos," Hendricks said. "All the Brewers fans were trying to cheer over them."
On deck: Jeff Samardzija will make his third spring start on Monday when the Cubs travel to Scottsdale to face the Giants. The 3:05 p.m. CT contest will be available for free via a Cubs.com exclusive audio webcast.
Samardzija will likely pitch at least four innings. In his last outing against the Rockies, he gave up three runs on four hits over three innings. So far, he has not walked a batter, which is good. The right-hander is working on being more efficient with his pitches.