Kash Patel pulled out some schoolyard-level debate tactics on Tuesday when he was grilled about allegedly drinking on the job.

During a Senate Appropriations Committee hearing Tuesday, Democratic Senator from Maryland Chris Van Hollen raised concerns about reports of the FBI director's alleged excessive drinking.

Patel tried to flip the script on Van Hollen ... talking over him, slamming him for meeting with Kilmar Abrego Garcia -- the Salvadoran man wrongfully deported by the U.S. government last year -- and accusing him of "slinging margaritas" and running up a $7K bar tab "on taxpayer dime."

Van Hollen was visibly fed up and -- when he was finally able to get a word in -- told Patel straight-up ... "The fact that you mentioned that indicates that you don't know what you are talking about."

Check out the video to see the whole thing play out.