Preheat the oven to 350 degrees and prepare the donut pan by spraying with non-stick spray. Set aside.
In a large mixing bowl, add the cake mix, 1/2 cup of sprinkles, oil, butter, and eggs. Using an electric hand mixer, blend until all ingredients are combined. Do not overmix - it will be thick.
Using a spoon, add the mixture to the donut pan. Even out by pressing down and working in a circular motion around each one.
Bake for 8-10 minutes or until beginning to brown.
Remove from oven and flip the donuts out onto a plate or dish to cool completely.
Once the cookies have cooled, add 1/4 cup of frosting to a microwave safe dish. Heat in 10 second increments until completely melted. Stir with a spoon between heating.
Drizzle the frosting over each donut in a zig-zag motion then top with remaining sprinkles.