Heat the oven to 350ºF. Grease a 12-cup muffin tin and set aside.
Combine flax and water and set aside to gel while you prepare the remaining ingredients if not using regular egg.
In a small bowl, whisk together bananas, milk, maple syrup and coconut oil. Whisk in flax egg or regular egg.
Add the dry ingredients directly into the bowl with the wet and whisk to thoroughly combine.
Fill each muffin cup ¾ of the way.
Top each muffin with a sprinkle of sugar in the raw.
Bake on the center rack for 20-24 minutes until the center springs back when touched lightly or when a cake tester inserted into the center comes out clean.
Cool in the muffin tin for 2 - 3 minutes, then transfer to a wire rack and cool completely or they will not set well and fall apart.