Call in the Brinks truck ... 'cause 2 Chainz just helped a group of streetballers collect a $25,000 check -- coaching the guys to victory in a huge hoops tourney in Miami. 

2 Chainz was one of 6 celebrity coaches at the South Beach Invitational in Miami ... which pitted some of the best street ballers from all over the country against each other in a tourney sponsored by the legendary Rucker Park. 

Check out the video -- 2 Chainz, a former college basketball player, clearly took his job seriously ... dishing out wisdom to his team as they took on squads coached by Pusha T, French Montana and other stars. 

In the end, 2 Chainz's team won the grand tourney and the grand prize -- a fat $25k check.