Combine milk, banana, oil, vanilla and vinegar in blender by blending on high for about 1 minute.
Combine dry and wet together in a bowl – stir well but do not over mix.
Fill each doughnut mold with the mixture - do not overfill as they will rise.
Bake for 15mins, check they are cooked through by inserting a skewer into the centre of the doughnut and checking it comes out clean. Once cooked, remove from the oven, brush with melted coconut oil, mix the cinnamon and coconut sugar in a bowl and sprinkle it on top of the doughnuts. Leave to cool for about 30mins before serving.