Blend the watermelon cubes in a blender until completely smooth, about 30 seconds.

Pour the blended watermelon through a fine mesh strainer into a pitcher, pressing with a spoon to push the juice through and leave the pulp behind.

Whisk the lime juice and honey into the strained watermelon juice until the honey fully dissolves.

Cover and chill the mixture for 20 minutes.

Fill eight glasses with ice.

Stir the chilled base once, then top the pitcher with the sparkling water, pouring slowly down the side.

Pour over the ice and garnish each glass with a mint sprig, lightly pressed between your fingers, and a small watermelon wedge on the rim.