Prepare an 8 x 8 baking dish by lining it with parchment paper and spraying the parchment paper with cooking spray. Set aside.
Open your watermelon sour patch kids.
Melt watermelon sour patch kids and 300 grams water on low - medium heat in a medium sized pot.
While the watermelon sour patch kids are melting, bloom your gelatin.
Bloom gelatin by whisking together 200 grams of cold water with 40 grams of unflavored gelatin in the mixing bowl of a 5 quart planetary mixer. Let it sit, undisturbed, until watermelon sour patch kids are melted.
The watermelon sour patch kids take A LONG TIME to melt. Once the mix thickens, and you notice the pieces starting to get smaller, you can run the gummies through the potato ricer to speed things along. Add the final 100 grams of water after this.
Once watermelon sour patch kids are melted, pour the syrup over the gelatin.
Turn the mixer on low for 30 seconds to combine the syrup and gelatin.
Increase the speed to high and let it mix for 8 minutes.
Turn off mixer. Pour watermelon sour patch kids marshmallows into prepared pan.
Top with additional watermelon sour patch kids if desired.
Place another piece of oiled parchment paper on top of the marshmallow, creating a seal.
Let watermelon sour patch kids marshmallows sit for 12 hours undisturbed before cutting.
After 12 hours, oil a sharp knife and cut marshmallows into desired size. 2" x 2" is recommended.
Toss marshmallows in powdered sugar.
Store in an airtight container.