Preheat oven to 425.
Combine cake mix, buttermilk, melted butter, and eggs and stir just until well mixed.
Transfer mixture to a zippered bag and cut off corner for piping.
Pipe into a donut pan filling each about 2/3 of the way but make sure it doesn't top center hole.
Bake about 8 minutes, until tops rebound when pressed.
Leave donut in pan for about 3 minutes.
Remove from pan and set on cooling rack.
In a small bowl just big enough to dip donuts, combine glaze ingredients and stir until smooth.
Dip top of donut in glaze.
Hold above bowl allowing excess to drip off.
Place donut on wax paper or return to cooling rack (glaze side up).
Decorate with sprinkles if desired.
Wait for glaze to set.