In another bowl, combine the sugars, vanilla, oat milk, apple cider, apple sauce, and apple cider vinegar. Stir with a whisk until combined and the sugar is slightly dissolved.
Combine the cinnamon and sugar on a small plate or shallow dish. Melt the coconut oil or vegan butter. Use a pastry brush to brush the tops (sides and bottoms if you want) of the doughnuts.