Cheat. Do not make bets with this man as you will lose, not because you actually lost but he will change the rules at the last moment and cheat his way to victory.
Gary: "I'll bet you a drink that 9 wins in deal or no deal"
Yas: "Yeah ok'
Deal or no deal: 6 wins!!!!!
Gary: "Yes 6! I said 6!!!! You owe me a drink!"