Preheat the oven to 350 °F (180 °C). Spray cooking oil in two 12-hole mini muffin pans. Set aside.
Whisk self-rising flour, brown sugar, and cinnamon in a large mixing bowl.
Add in apple cider vinegar and oil.
Stir to combine and form a smooth batter.
Fill each mini muffin hole up to ¾ of their level.
Bake the donut holes on the center rack at 350 °F (180 °C) for 18-20 minutes until they are golden brown and a toothpick inserted in the center comes out clean.
Let the donuts cool in the pan for 10 minutes, then flip them upside down on a cooling rack and let them cool for 20 minutes.
Meanwhile, in a small bowl, prepare the cinnamon sugar for coating the donut hole. Whisk cinnamon and sugar. Set aside.
Using a pastry brush, brush the donut holes with melted vegan butter, then roll them in cinnamon sugar to coat.
Repeat until they are all coated and look like mini donut holes.
