Preheat oven to 350 degrees Fahrenheit. Line a baking sheet with parchment paper. Place the tapioca starch and water in a small bowl or liquid measuring cup. Stir to combine and allow to sit for a couple minutes.
In a medium bowl, combine organic cane sugar and maple syrup. Whisk to combine. Whisk in vegan butter, followed by tapioca starch slurry and vanilla extract.
Add the almond flour, white rice flour, baking soda, and salt. Stir until ingredients are completely incorporated. If needed, use your hands to thoroughly combine ingredients into a cohesive cookie dough.
Fold in ¼ cup of the rainbow sprinkles into the cookie dough. Place the remaining sprinkles on a plate.
Use a tablespoon to scoop out dough, then roll into a ball. Place ball on plate with sprinkles, roll to coat, then place on prepared baking sheet. Space cookie dough balls about an 1 ½ inches apart. Repeat until cookie sheet is filled with even rows.
Using your palm or the bottom of a glass, press each dough ball down about halfway.
Bake for 10-12 minutes, or until cookies are set on the outside. Allow cookies to cool on baking sheet for 4-5 minutes then transfer to a wire rack to cool.
Store at room temperature in an airtight container for 3-4 days.