You flip a coin to see who gets to go first; whoever loses has to perform oral on the other person for ten minutes straight (set a timer!) The goal of the game is to make the other person cum first.
If, in the first ten minutes, the person does not cum, you switch positions and go for another ten minutes. And if the second person doesn’t cum, you go back to the original position for ten minutes. So on and so forth until someone loses by cumming.
Loser has to buy dinner and finish the other person off in whatever manner they choose.