I was in the sun for a bit too long today, and i have a formal even tomorrow and i was wondering what is a good way to get rid of sun burn overnight?

Not really: Doubt any meds will improve burnt skin that fast. Also note that the skin will burn much easier for the next several months and you should use sun protection

Can't undo a burn: You probably already know the answer - you cannot get rid of the burn overnight but management should include moisturizing creams for the milder burns and for the more severe burns you may need a prescription cream. Camouflage make-up may be your best option if you have non-blistered sunburns. Prevention is the best form of treatment in these cases.