Watermelon Daiquiri on the Rocks: A watermelon daiquiri brings together fresh watermelon juice, white rum, and lime juice. Served on the rocks, this refreshing cocktail is perfect for late summer. This easy step-by-step recipe will show you how to make homemade watermelon juice, using either a juicer or blender, and then use a cocktail shaker to make this simple, but impressive and delicious summer alcoholic beverage.