This beautifully colored sipper elevates your neighborhood lemonade stand. Be sure to taste the watermelon first. If it's very sweet, reduce the sugar. Offer some refreshment to the planet and economy by going organic and local when you can.
Working in batches as necessary, purée the watermelon and lemon juice in a blender until smooth and transfer to a large container. Add the water and sugar and stir until dissolved. Pour over ice in tall glasses, garnish with mint and thin slices of watermelon, if desired, and serve.