Cut open your watermelon and set aside about a ⅓ to be used for your sangria fruit. Juice the other ⅔. If you don't have a juicer, simply put chunks of your watermelon in a food processor and chop it up till it's nothing but mush. Pour it into a mesh strainer over a bowl, and gently press it with a big spoon. You won't get every drop of the juice out, but you'll get a lot of it! Set it aside.
Chop and add your fruit. Make sure to chop your apple, pineapple and peach into tiny pieces. A lovely idea is to ball your watermelon. It just looks so pretty in your guest's glasses! Place all the fruit in a large pitcher.
Add the white rum, Triple Sec, Malibu and watermelon juice to the pitcher with your fruit and stir. Allow to sit overnight.
If you're adding a prosecco sparkle, add ½ bottle to your pitcher just before serving, and gently stir.
You'll require a large pitcher, fruit juicer (or food processor and mesh strainer) for this recipe.