How does one of the biggest young superstars in baseball celebrate his birthday?? Boat party turnup in Miami with his teammates, of course!!

Cody Bellinger and his fellow Dodgers friends hit the deck for his 22nd birthday Thursday ... taking advantage of their extra time in South Beach following the All-Star break to down some brews on the water.

Justin Turner appeared to throw the shindig for Belly ... with Alex Wood, Corey Seager and all their significant others joining in on the fun.

The highlight of the party -- the baseball bros actually had Jeremih's "Birthday Sex" song playing in the background as Bellinger blew out his birthday candles.

"... Girl, you know I-I-I!!!!!"