Preheat oven to 350°F. Grease or line 10 cups of a muffin pan and set aside.
Make cinnamon sugar: In a small bowl, mix together coconut sugar and cinnamon and set aside.
Make the snickerdoodle topping: Cream together softened coconut oil and coconut sugar. Stir in vanilla.
Add in oat flour, cream of tartar, baking soda, and a pinch of salt and mix until a crumbly, slightly sticky dough forms. Cover and store in fridge while you prepare the muffins.
Make the muffin batter: In a large bowl, mix together mashed bananas, maple syrup, almond butter, vinegar, milk, and vanilla extract.
Sift in flour, baking soda, and cinnamon. Use a rubber spatula to gently fold the dry ingredients into the wet ingredients. Mix until ingredients are just combined and no flour pockets remain. Be sure to scrape down the sides and the bottom of the bowl for dry flour.
Distribute the batter into the greased muffin cups, filling about ¾ full. Take the snickerdoodle topping out of the fridge and crumble over the muffins. Sprinkle cinnamon sugar on top. Bake 28-30 minutes, or until a toothpick inserted in the center of a muffin comes out clean.
Let the muffins cool for about 5 minutes in the pan, then gently remove and place the muffins on a cooling rack. Cool completely before serving.