For Watermelon cordial: 1 medium-sized watermelon, 1 quart of Thai basil simple syrup, 3 bar spoons of citric acid, 1 oz. grenadine (for color).
Cut watermelon and puree it in a blender. Then strain the watermelon puree. Stir in basil simple syrup, 3 bar spoons of citric acid, grenadine and stir it all together. Will keep it for up to 10 days in the refrigerator.