In a small saucepan over medium-low heat, add 1/2 cup granulated sugar and 1/2 cup water. Stir to combine. Gently heat the mixture until the sugar dissolves in the water. Once dissolved, remove from heat and add in a handful of fresh basil. Bruise the basil to release the natural oils. Allow the mixture to cool completely, then strain out basil leaves and pour syrup in an airtight container.

Add watermelon cubes to blender and blend completely. Work in batches depending on the amount of watermelon and size of blender. Once watermelon is blended, strain using a fine mesh sieve to remove pulp. After all watermelon has been blended and strained, mix with the juice of one lime and pour into an airtight container.

In a tall carafe, combine 3 cups watermelon juice with 4 ounces basil simple syrup. Add more or less of the basil simple syrup depending on desired sweetness.

In a short glass, add 2 ounces of the Watermelon Basil Mixer and top with sparkling water. Garnish with a watermelon cube and basil leaf. Serve immediately.