How to Make It
Combine first 6 ingredients in a small saucepan over medium-high heat. Bring to a boil; reduce heat to medium-low, and simmer 14 minutes or until liquid is slightly syrupy, stirring occasionally to break up grapes. Cool completely. Remove and discard orange rind and rosemary. Place grape mixture in a blender or food processer. Pulse until coarsely chopped. Strain liquid through a fine sieve over a bowl, pressing gently to extract liquid from solids; discard solids.
To prepare each cocktail, place 1/4 cup grape mixture in an ice-filled glass. Add 1/2 cup tonic water, 1/4 cup club soda, and 1 tablespoon orange juice. Garnish each drink with a rosemary sprig.