I've been experimenting with gluten free yellow cake mix recently, specifically the one from Hodgson Mill, so I wondered about GF cake donuts from a mix. Turns out there are several versions out there. The one I followed (using regular cake mix) is HERE, and I got good results by just subbing the GF mix in a comparable size. My GF tasters (three generations of ladies, starting with a picky four year old) found them to be deliciously moist and not at all grainy (like so many GF products). They especially liked the glaze I made with 2 cups of powdered sugar and five little servings of hazelnut flavored half and half--30 seconds in the microwave makes it liquid enough to use as a glaze.
We all agreed that they could have been baked longer than the recipe called for, as they were fully baked but fell apart easily. I also added a quarter teaspoon of nutmeg (a classic donut flavoring) to the dry ingredients before mixing in the wet.