If you are juicing a real watermelon, place pieces into a blender and blend until it's juice like. Strain the pulp (as much as you can).
Combine Watermelon Margarita, watermelon juice, lemon juice and basil leaves in a pitcher and place in fridge for about 2 hours. ⠀
When ready to serve, combine 2 parts Watermelon blend with 1 part sprit over ice. Swirl to combine. Top with soda water (optional). Garnish with a lime, and serve!