Standing at the fountain in future world, looking toward the international showcase... look at the building ahead and to your right and you'll see a fake ice facade with some sort of snow vehicle there, if I recall it correctly. You go in through a cold tunnel with a snow machine or two running and come into the drink sample area.
All the samples are free. Some folks use that excuse to fill their drink cups while they are there, but I figure that's kind of poor form.