Any of the margaritas or tequila flights at La Cava de Tequila. Don't even think about touching the margarita stand outside - they are sugar water compared to the Cava margaritas. They are all worth a try! Also, if you've got a strong stomach, go for the Aquavit in Norway, it comes as a shot.
If you ever have more than just one day to spend in Epcot, you can always try a drink in each country! Responsibly, of course
I'll also throw in the plum sake at Tokyo Dining in the Japan pavilion, and they have this delightful red currant sparkling wine at Chefs de France, but I can't remember the drink's actual name.