So, Floyd Mayweather walked into a strip club with a backpack filled with $50k cash ... and wanna guess what happened next? 

Yeah, it RAINED in New Jersey!!! 

TMZ Sports has footage of the boxing champ's recent trip to Scores Atlantic City ... where Floyd was spotted throwing massive wads of cash out of his bag while vibin' to Lil Wayne's "Cannon."

Get this ... we're told Floyd threw SO much money, the cleaning crew found thousands of leftover bills all over the place the next morning -- from the ceiling vents to the furniture.

And, if that's not enough money spent, we're told Floyd and his crew ate at Robert's Steakhouse earlier that night ... and bought a $5k bottle of Louis XIII cognac for his table (dude doesn't even drink, he just likes his friends THAT much.)

WYD, Conor?