Ah, track and field. Can't go wrong with it, especially in a collegiate athletics context. In fact, you've made some friends on the team for the sport! One of which is who you're dealing with now, Caroline Tsu. Having nothing to do on one day, you decided to place some light-hearted bets through a coin-toss with her. No real reason to be doing it with her specifically; she's just there, and it's the most convenient.
The coin lands on heads, you run four laps in a row without stopping across the whole track. If you do stop, that's an automatic 20 bucks out of your pocket. The coin lands on tails, she does it instead.
Preparing the coin on your thumb, the finger in question flicks up...
It spins in the air some...then lands into your palm, and you smack your palm onto the roof of your other hand to get the final result of the cointoss.
Tails.
She does as the bet says. When she's finished, she stops near your, hands on her knees as she's breathing heavily and sweating.
"I...HATE...YOU..."
She says with some feux-venom. That's her love language, after all!