Combine the sweet rice flour and sugar in a microwave-safe bowl. Mix them well.

Pour in the strained watermelon juice. Whisk the mixture until it is smooth and there are no lumps.

Cover the bowl loosely with plastic wrap, leaving a small vent. Microwave on high for 1 minute.

Remove the bowl and stir the mixture thoroughly with a wet spatula. The mixture will start to thicken.

Re-cover and microwave for another 1 minute. Stir again. The dough should be very thick and sticky.

Cover and microwave for a final 30 seconds to 1 minute, or until the dough is translucent and fully cooked.

Generously dust a clean work surface with cornstarch or potato starch.

Scrape the hot mochi dough onto the prepared surface. Dust the top of the dough lightly with more starch.

Allow the dough to cool slightly until you can handle it comfortably.

Using a rolling pin dusted with starch, gently roll the dough out to about 1/4 inch thickness.

Use a small, round cookie cutter or the rim of a glass to cut out bite-sized circles. This makes your homemade mochi bites.

Serve these refreshing watermelon treats immediately, or store them covered in the refrigerator.