I am not sure about the buffets, but at the garden grille at the land in epcot the drinks are included. this is a super place to eat. it is all you can eat served family style. that means you are served at you table by a waitstaff, but they will bring as much as you want. it is also like that at whispering canyon cafe at the wilderness lodge, and I think drinks were included in the price there, but only if you get the all-you-can-eat deal. ( you have a choice of this or a regular meal at WCC, not at GG) .
Go to DebWills site and if you look up in dining, she has the updated menus for all the restaurants in Disney. Entree and prices are listed as well as items included on the buffets.