Step 1

Place huckleberries in a 1-qt. jar. Bring sugar and vinegar to a boil in a small saucepan, stirring to dissolve sugar.

Step 2

Pour hot vinegar mixture over berries and mix with a fork, crushing berries gently to release more flavor. Seal jar and store in a cool dark place 4 days.

Step 3

Strain shrub through a fine-mesh sieve lined with cheesecloth into a clean jar; cover and chill. Check shrub every week or so until vinegar flavor mellows to your liking.

Step 4

For each drink, combine 3 Tbsp. shrub with 1 cup club soda in a glass filled with ice. Taste and add more shrub if you like.

Step 5

Do Ahead: Shrub can be made 6 months ahead. Keep chilled.