Combine plant based milk with apple vinegar in a small bowl. Set aside to thicken. This is your vegan buttermilk.
Add the rolled oats, cinnamon, baking powder and salt to the blender and blitz until a fine flour is formed.
Add the vegan buttermilk, chopped bananas and vanilla to the blender and blend until a smooth batter is formed, scraping down the sides as necessary.
Grease and preheat waffle iron. Use ⅓ cup of batter for every 4 inch waffle. Use ½ cup of batter for every 7 inch waffle and 1 cup of batter for a 9 inch waffle. The waffles are done when there is no steam coming out of the waffle maker and the waffles are crispy and golden.