Every year for Halloween we make homemade root beer in a witch's cauldron. It's easy, fun and oh so impressive to your little goblins and ghosts. Even though it's easy, many people ask how it's done. The tricky thing back east has been finding root beer extract and dry ice. You have to buy your dry ice no more than a couple of hours before using, as it loses volume quickly.
5 lbs. sugar
5 gallons water
7 lbs. dry ice
Mix water, sugar and root beer extract until sugar is mostly mixed in and dissolved. Add half of the dry ice at once. Constantly stir so the dry ice doesn't pile up in the bottom. After about 20-30 minutes it should be sufficiently carbonated. I usually hold back and add more dry ice here and there to make the smoke for the kids.