How to Make It
Stir together sugar and boiling water until sugar is dissolved. Stir in cold water, lemon zest, and juice. Pour into ice cube trays, and freeze until solid, about 8 hours.
Process 2 cups frozen lemonade cubes, blueberries, and vodka in a blender until smooth. Stir in chilled club soda. Pour into glasses; garnish with lemon slices. Serve immediately.