Pour black sugar onto a small plate. Rub a lime wedge along the rim of each serving glass and dip in sugar to coat.
Add ice cubes to the serving glasses.
In a cocktail shaker, combine grape juice, orange juice, lime juice, cranberry juice, coconut milk (if using), and simple syrup.
Shake well for about 10 seconds.
Strain the mixture evenly into the glasses.
Top each glass with lemon-lime soda or ginger ale for fizz.
Stir gently to combine.
Garnish with skewered grapes, blueberries, or blackberries, and a cinnamon stick if desired.
Carefully add a small piece of dry ice to each glass using tongs (optional and for visual effect only—do not ingest).
Serve immediately while bubbly and cold.