The Giants released Sandoval on Thursday.
Sandoval signed a minor-league contract with the Giants on Saturday that includes an invitation to major-league spring training, Andrew Baggarly of The Athletic reports.
Sandoval signed a contract with the Mexican League's Acereros De Monclava on Monday.
Sandoval (personal) was reinstated from the restricted list Thursday.
Sandoval was placed on the restricted list for an unspecified reason Tuesday.
Sandoval flew out as a pinch hitter in Tuesday's loss to the Mets.
Sandoval went 3-for-4 with a run scored in Tuesday's win over the Red Sox.
Sandoval hit a two-run, pinch-hit home run in a 2-0 win over the Nationals during the second game of Wednesday's doubleheader.
Sandoval hit a two-run home run in his only plate appearance Thursday against the Phillies.
Sandoval's contract was selected by Atlanta on Saturday.