Preheat the oven to 350°F (175°C) and lightly grease a standard 6-cavity donut pan.
Combine the almond milk and apple cider vinegar in a small vessel; let stand for 5 minutes to create vegan buttermilk.
Whisk the flour, 1/2 cup sugar, baking powder, salt, and 1/2 tsp cinnamon in a large mixing bowl.
Incorporate the applesauce, 2 tbsp melted vegan butter, vanilla extract, and the buttermilk mixture into the dry ingredients.
Whisk until the batter is smooth, taking care not to overmix to maintain a light texture.
Transfer the batter to a piping bag and fill each donut cavity approximately 3/4 full.
Bake for 10 to 12 minutes until the donuts are springy to the touch and a toothpick comes out clean.
Cool the donuts in the pan for 5 minutes before transferring them to a cooling rack.
Whisk the coating sugar and 1 tbsp cinnamon together in a shallow bowl.
While slightly warm, brush each donut with melted vegan butter and immediately toss in the cinnamon sugar mixture to coat.