Add blackberries and sage leaves to the cocktail shaker. Muddle until the berries release their juice.
Pour in the lime juice and simple syrup. Fill the shaker with ice cubes.
Shake for 15-20 seconds until the mixture is well chilled.
Strain the mixture into tall glasses filled with ice. Top each glass with sparkling water.
Stir gently to combine. Garnish with fresh blackberries and sage leaves.
Notes
Store any leftover mixture in the fridge for up to 2 days without the sparkling water.Fresh berries work best, but frozen blackberries can work in a pinch. Thaw them first.Adjust the simple syrup amount based on the sweetness of the berries.Make a sugar-free version by replacing simple syrup with a natural sweetener.This recipe makes 4 servings.