Start by preheating your oven to 350°F (175°C). Lightly grease each cavity of a doughnut pan with cooking spray or a small amount of oil to prevent sticking.
In a large mixing bowl, combine the sweet rice flour, granulated sugar, and baking powder. Whisk these dry ingredients together thoroughly to eliminate any lumps and ensure even distribution.
In a separate medium bowl, whisk together the milk, egg, vanilla extract, and melted coconut oil until the mixture is smooth and fully blended.
Gradually pour the wet mixture into the dry ingredients. Stir gently until you achieve a smooth batter with no visible lumps. It's important not to overmix, as this could affect the texture of your doughnuts.
With the help of a spoon or piping bag, carefully fill each mold of the doughnut pan with the batter, filling each one about 3/4 full to allow room for rising.
Place the filled pan in the preheated oven and bake for 12-15 minutes. The doughnuts are ready when they spring back lightly when pressed with a finger.
After baking, let the doughnuts cool in the pan for about 5 minutes. Then, gently transfer them to a wire rack to cool completely.
While the doughnuts are cooling, you can prepare the glaze. In a small bowl, whisk together the powdered sugar and water until the mixture is smooth and free of lumps. If you’d like, add a few drops of food coloring to personalize your glaze.
Once the doughnuts are completely cooled, dip the tops into the glaze, allowing any excess to drip off back into the bowl.
For the finishing touch, sprinkle colorful sprinkles over the glazed tops immediately before the glaze sets. Allow the glaze to set for a few minutes before serving for the best texture.
Notes
For a richer flavor, use unsalted butter instead of coconut oil.