Chill everything. Cold ingredients make the best mocktail.
Pop your watermelon, limes, and sparkling water in the fridge ahead of time.
Blend the base. Add watermelon cubes, lime juice, honey or agave, and a few mint leaves to a blender. Blend until silky smooth.
Strain (optional). If you prefer a smoother drink, pour the mixture through a fine mesh strainer into a pitcher. If you like it pulpy, skip this step.
Taste and adjust. Add more lime for brightness, more sweetener for balance, or a tiny pinch of salt to make the flavors pop.
Build the drink. Fill glasses with ice.
Pour the watermelon mixture halfway up the glass. Top with chilled sparkling water and stir gently.
Garnish. Smack a mint sprig between your hands to release aroma, then add it to each glass. Lime wheels or thin watermelon wedges look great, too.
Serve right away. Enjoy while it’s cold and bubbly.