Preheat oven to 350 degrees. Spray two - 6 count donut pans with cooking spray.
Pour the cereal into a baking pan and cook for 7 – 8 minutes or just until fragrant. Let cool.
Combine the flour, baking powder, and salt in a large mixing bowl. In another mixing bowl, whisk the eggs, add 1 cup of Zero sweetener, the agave, 2 teaspoons vanilla and ½ cup rice milk. Whisk to combine, add to the flour mixture and mix well. Add 1 cup of the toasted cereal to the batter and stir.
Fill the donut pans about 2/3 full and bake for 13 – 15 minutes or until they are firm to the touch and a toothpick inserted into the center of a donut comes out clean. Let cool in the pan for 5 minutes then remove to a wire rack to finish cooling. You may need to run a knife around the edges to help remove (especially if you fill them too full).
Place the remaining cup of Zero into a blender with the corn or tapioca starch. Blend on high speed until it resembles powdered sugar. Pour into a mixing bowl; add the remaining teaspoon of vanilla and remaining ¼ cup of rice milk. Stir until it turns into a thick frosting (you may need to add a drop or two more of rice milk if it is too thick – it should be spreadable).
Frost each donut and then dip the frosted side into the remaining cereal.
These donuts are best eaten the day they are made.