Preheat oven to 350 degrees. Mix egg, banana, pumpkin, water, and vanilla together in a bowl. Add in oats, cinnamon, cocoa, baking powder, salt, instant coffee, and stevia. Mix well with wet ingredients. Spray a 12 and 6 capacity muffin tin with cooking spray or use cupcake liners. Pour mixture evenly into muffin tin cups. Bake 35 minutes until a toothpick in center comes out clean. Cool and enjoy or freeze them in gallon freezer bags.