In your stand mixer with the paddle attachment, combine the coconut oil, non-dairy milk, aquafaba, maple syrup, pumpkin and vanilla. Beat on medium until blended, 3 minutes. Add brown sugar and beat for another few minutes.
In a medium bowl, combine the dry ingredients. With the mixer on its lowest setting, slowly add the dry mixture to the wet, a little at a time, until it's all incorporated. Stop the mixer, scrape down the sides and mix again.
Scoop the mixture into a piping bag or a large zip-top bag, and close it up. Smush all the batter down into one corner of the bag (I use my bench scraper for this), and snip off the corner of the bag.
Spray your donut pans with oil, or use a pastry brush to grease them. Pipe the donut batter into the pans, then bake at 350 degrees for about 10-12 minutes, until the tops are firm.
Allow them to set up and cool in the pan for a few minutes, then run a small offset spatula around the edges of the donuts and pop them out onto a cooling rack.
Meanwhile, combine the sugar and cinnamon in a flat-bottomed bowl. Brush each of the donuts with melted vegan butter on both sides, then drop them into the cinnamon sugar. Flip to coat. Transfer to a wire rack, and repeat for the remaining donuts.