In a pitcher, combine the coconut water, lemon juice, calamansi lime juice, and sugar. Stir to mix well. Add the sliced lemons and ice to the pitcher. Pour the lemonade into glasses and garnish with mint leaves.
Notes
I used Kimbo Young Coconut Juice with pulp and strained out the pulp. You may skip the calamansi lime if you don't have it. They are the fruits from the calamondin tree. They are available in Southeast Asian stores or Filipino food stores.