Preparation

Make the shrub

• In a 4-quart saucepan, combine the cranberries, sugar, vinegar, and lime zest with 3 cups of water and bring to a boil over medium-high heat. Reduce the heat to low, cover, and simmer until the cranberries are completely broken down, about 20 minutes. Let cool.
• Purée with an immersion blender. Strain through a fine sieve set over a large bowl, pressing hard on the solids to extract as much liquid as possible.

Make the sparklers

• Per drink, combine 3 to 4 Tbs. of the chilled shrub with cold seltzer (and vodka, if you like).

Make Ahead Tips

The shrub will keep, refrigerated in a jar, for up to 2 months.