Lil Xan is bringing the beef to Supreme Patty … throwing a drink and igniting a wild bar brawl.

The rapper was performing at Treehouse Rooftop Lounge in Fort Myers, FL when things got heated in the VIP section. Our sources say Xan and Internet prankster SP exchanged some heated words — you can see Xan was up on a stage or platform while he and Patty jawed at each other.

But, when Xan threw his drink at Supreme Patty, around 1:30 AM Sunday, the talk stopped and Patty came charging right at Xan before getting pulled back.

As for what set them off, Lil Xan claims Supreme Patty tried mooching off his group’s bottle service — and Patty says he was just defending himself after getting a drink thrown at him.

We’re told the cops weren’t called and both parties left shortly after the scuffle.

The beef doesn’t appear to be squashed yet … they’ve been dissing each other on social media ever since the weekend scrap. No word if Xan is working on a diss track, but chances are …