The 30-year-old Sandoval spent his first seven major league seasons with San Francisco (2008-14), winning World Series titles with the Giants in 2010, 2012 and 2014. Sandoval will report to Class A San Jose.
Sandoval was the 2012 World Series MVP with the Giants but struggled since leaving San Francisco for Boston as a free agent. He signed a five-year, $95 million contract after the 2014 season and was released by the Red Sox on Wednesday when he did not report after being designated for assignment.
Injuries and poor performance plagued Sandoval in Boston. He hit .245 with 10 home runs and 47 RBIs in 2015, played in only three games in 2016, and batted only .212 with four homers and 12 RBIs in 32 games with the Red Sox this season. Sandoval left San Francisco on bad terms after the 2014 season, claiming the team disrespected him during contract negotiations leading up to his departure.
Bryant sprained his little finger on his left hand in a headfirst slide in the first inning of Chicago's 8-2 victory over the Braves at Atlanta on Wednesday. X-rays were negative, but the 25-year-old was experiencing soreness while gripping the bat.
Cubs manager Joe Maddon on Friday expressed doubt about Bryant playing Saturday. He batted second and played third base.
Bryant is coming off a National League MVP season when he helped the Cubs to their first World Series title since 1908.
Sogard, 31, sustained a left ankle strain in late June and has not played since July 4. He is batting .331 with three home runs and 14 RBIs in 43 games this season.
Broxton, 27, has gone hitless in his last five games while striking out seven times in 12 at-bats. He was forced out of the starting lineup because of his slump for Friday night's 6-1 loss to the Philadelphia Phillies. He struck out on three pitches as a pinch hitter.
Broxton is batting .218 with 14 home runs, 36 RBIs, 17 stolen bases and 124 strikeouts in 293 at-bats this season.