First of all Happy Birthday!!

Last year was the first time I had gone to Disney since turning 21 (I'm 25 now). I had gone multiple times as a kid and teenager but to be officially an adult at the park is awesome! Of course my suggestion would be to drink the best drinks at Disney.
If you can get a reservation at Be Our Guest do it! Not only is it gorgeous inside (seriously breath taking) but its the only place in Magic Kingdom you can get a glass of wine or two. Its a little pricey but definitely worth it
And of course we can't mention drinking at Disney without mentioning Epcot. If Drinking around the World isn't your style- I'd say at least try some of these drinks:
Mexico- La Cava Del Tequila- Any of their specialty margaritas. They have a lot of different and unique kinds. They have a jalapeno one, a cucumber one, an avocado one (I had this one- Yum!) some fruity ones and more. It's also cool to go on the boat ride with a bit of a buzz
Germany- Beirgaten- The Beer Flight (Schöfferhofer Pink Grapefruit Hefeweizen, Warsteiner Dunkel, Schöfferhofer Hefeweizen, Altenmünster Oktoberfest)
Japan-Mitsukoshi- Don't just try the first stand you see, they have a Sake Bar in the very back of the shop. My favorite is the Nigori, an unfiltered milky sake.
France- The Slushie stand. My favorite thing here, especially on a really hot day you can end up drinking 5 of these since they are so refreshing. The Grand Marnier Orange Slush. Out of everything I'll mention def try this one if nothing else!
Finally I'd like to end it off with a Guinness at the Rose and Crown in the UK.
Happy Boozing!
