Preheat oven to 350°F. Spray donut pan with non-stick spray.
Whisk dry donut ingredients together in a large bowl.
Mix wet ingredients in another bowl, then combine with dry. Stir until just mixed.
Fill donut pan cavities 3/4 full with batter. Bake 11-12 minutes, until a toothpick is clean. Cool on rack.
For glaze, whisk powdered sugar and cocoa powder. Add melted butter and vanilla. Slowly add hot water to desired consistency.
Dip donut tops in glaze and let excess drip off. Set on wire rack; allow glaze to set.