Betta in fish bowl not eating

Ηi all,

I got a betta fish from the local store yesterday and a fish bowl of around 8 liters. Unfortunately I was not well informed to know that bettas (as well as any other fish) should not be in fish bowl and I am planning to buy my betta a proper aquarium tomorrow. Any suggestions on how to keep the little guy safe until i set the new aquarium up? My fish has stopped swimming around and has not eaten any of the food today and is swimming slowly on the surface.