This is a perfect way to use up some of a giant watermelon and is also a wonderful way to help the kids stay hydrated in the warmer months. You can scale the recipe up or down to make more or less as you like.
Blend, starting on low and increasing the speed to high as the cubes start turning into juice.
Strain through a fine-mesh sieve if desired.
Serve immediately or store in the fridge and serve within 2-3 days.
Notes
Seedless watermelon is easiest here.
If using watermelon with seeds, you'll want to run the blender slowly to avoid crushing up the seeds. Once most of the melon cubes are blended and crushed, you can strain the juice through a fine-mesh strainer to remove the seeds.
This works with any color of watermelon you may find at the store or farmer's market.
If you want the juice to be cold, refrigerate the melon before you blend it.
Offer in a straw cup or a small open cup with a straw.
Without a blender: Add the cubes to a zip top storage bag, seal it, and use hands to mash up the melon to make juice. Strain through a fine mesh strainer placed over a bowl. This is fun to do with the kids!