Loads of places switched to coffee pods for the free coffee. Those things often run like $0.40-$0.50/ea for name brand varieties, not including the cost of water filters and what not. Probably cheaper per unit if you just serve large carafes of it.

A 12oz soda from a soda fountain has a marginal cost of like $0.10. Even then cans of soda can be had wholesale for ~<$0.50, especially off-brand varieties.