Think back to that last gin and tonic you ordered. Remember how it started out so crisp, effervescent, and refreshing? Now fast-forward to the last few sips. That’s right: flat, diluted, muddied with melted ice. To keep the frizzante fresh and rollicking from start to finish, a few local bartenders have taken to carbonating the entire cocktail in single-serve bottles, changing the game of bubbly boozing for the better. Here’s how they do it.