In an upright blender, combine the watermelon and strawberries. Turn the blender on to high and let the fruit liquify completely. This should take no longer than 30 seconds.

Set a fine mesh strainer over a wide pitcher or a bowl that easy to pour out of. Pour the watermelon and strawberry juice base out into the strainer, working in two batches. Use a spoon to scrape the bottom of the strainer to get all the juice base through.

Once you’ve run all of the fruit puree through the fine mesh strainer, rinse out the blender pitcher. Return the juice base to the blender and add the lime juice and agave nectar. Blend this mixture on high until combined, about 10 seconds.

Fill glasses with ice. Pour the juice base into the glasses to fill them by one third. Top the juice base with sparkling water. Enjoy the sparkling strawberry watermelon limeade with garnishes such as: fresh mint or lemon balm leaves, lime wedges, or slices of watermelon. Enjoy immediately!