Cruz, who was second in the Majors last season with 44 homers, went 1-for-4 to put his spring average at .103 (3-for-29), but he's hit two homers in the past four days and appears to be getting his timing down.
"Those were probably the best swings he's taken all spring today," Mariners manager Scott Servais said of Cruz.
Iwakuma, who returned to Seattle in the winter after a tentative deal with the Dodgers unraveled because of a failed physical, allowed three runs on eight hits in 4 1/3 innings, with three strikeouts and one walk.
Cruz's home run to left came after a walk to Marte, a single by Sardinas and a double-steal.
Up next for the Mariners: Seattle has its first off-day of the spring on Tuesday, but left-hander James Paxton will throw in a Minor League game at 1 p.m. PT at the Peoria Complex to get his regular work in. The rest of the squad will return to Cactus League play on Wednesday in a 7:10 p.m. PT game against the A's in Peoria, Ariz., with right-hander Nathan Karns getting the start as he and Paxton continue battling for the fifth-starter spot.
Up next for the Dodgers: The Dodgers travel to Surprise, Ariz., for a 6:10 p.m. PT game against the Royals on Tuesday, with Alex Wood starting for L.A. and Chris Young for Kansas City. Among the relievers likely to pitch is former Royals right-hander Louis Coleman, who hasn't allowed a run this spring and is in the running to make the Opening Day roster.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.