This is both refreshing and fun. You can substitute the sparkling water with soda for a sweeter taste. The rum can be eliminated for a non-alcoholic alternative. The combination of the watermelon and lime is so refreshing.
Muddle the mint leaves, lime slices and sugar together and pour in glass. Pour the lime juice, watermelon juice, rum and club soda into the glass. Add the ice cubes and stir. If you like your drinks super sweet, substitute lemon/lime soda for the club soda.