"Shark Tank" shark Kevin O'Leary dropped $13,000 at Bagatelle Miami Beach Thursday night to help his friend celebrate a birthday.

Kevin treated his crew of 7 to a 500gr of Osetra Caviar -- for a measly $6,000. His crew then devoured ribeye steak, turbot fillet and cake.

As for what rich people do when they're thirsty ... they drink $1,000 Magnum Perrier-Jouet Belle Epoque Rose bottles delivered by servers dressed as Superman and Supergirl. Duh!

Earlier this week he told us on "TMZ Live" how winners can protect their Powerball jackpot.