1/4 cup blackberries
2 fresh sage leaves
2 cups plus 1 tbsp. cold sparkling water
Put blackberries and sage in a large cocktail shaker. Add 1 tbsp. water; mash well with a muddler or end of a wooden spoon.
Stir in sparkling water, cover, then strain into an ice-filled glass (for a clearer drink, pour through cheesecloth).