Post Malone is out here rapping Cowboys victories into existence -- and with a crazy win over the Giants, he celebrated in the best way possible ... making the other guy wear your team's gear.
The Texas native was at the Cowboys/Giants game Sunday in NY, where he was surrounded by Giants fans ... one of whom we're told he made a bet with. It was simple -- if my Cowboys win, ya gotta rock my Cowboys jacket. Well, they won all right ... in epic fashion.
Cole Beasley. WOW.
(via @dallascowboys) pic.