The Giants assigned Alcantara to their minor-league camp Monday.
Alcantara signed a minor-league deal with the Giants on Friday, Maria I. Guardado of MLB.com reports.
Alcantara will be part of the Angels' 60-man roster.
Alcantara signed a minor-league deal that includes an invitation to spring training with the Angels on Tuesday, Fabian Ardaya of The Athletic reports.
Alcantara signed a minor-league contract with the Mets.
Alcantara cleared waivers and was sent outright to Double-A Pensacola on Monday, Zach Buchanan of the Cincinnati Enquirer reports.
Alcantara was designated for assignment by the Reds on Saturday.
Alcantara is hitting .191/.200/.277 with 33 strikeouts in 94 at-bats as a utility player with Cincinnati this season.
Alcantara has a .213/.222/.313 slash line with one home run in 81 plate appearances this season.
Alcantara went 1-for-4 with a two-run home run during Sunday's loss to Atlanta.