[Maybe]

Really for 5 miles it doesn't matter all that much in my opinion. Assuming you don't run often (and it seems like you don't or this bet would be easy money for you), make sure not to eat too much at all before the run. I'd actually do the run in the morning and not eat more then half a banana or a bottle of Gatorade; anything more and cramps could kill you.

The night before really doesn't matter too much either for a run this short. If you don't get wasted, don't eat anything crazy that will upset your stomach, and stay hydrated it should be cake.