Why not have Coke and Pepsi like all non-soft drink owned eating joints and all Grocery stores have?
I don't think I've ever seen a restaurant that offers both. while im sure they exist somewhere, I would bet that at least 98% of all restaurants, snack bars, etc. Have an exclusive deal with one or another bottling company. Generally the local bottling company offers the machine and servicing of the machine for free, in return for the exclusive agreement. (At least that's how it works down here in the south!).