You can get so very creative with these donut monsters & make them all sorts of ways. There really is no wrong way, use your imagination! Here are a few ideas to ideas though to get your started.
Color frosting & melted almond bark with food coloring color(s) of your choice.
Cut the very ends of the donuts off, making an upside down "U" shape. Use frosting or melted almond bark to glue cookies or mini donuts to the cut ends, making feet. You could stick the white part from candy corns in to give them 'toes' too if you wanted.
Use toothpicks & gummy eyes to give eyes with height - or cookie icing along with small, candy eyeballs to put the eyes on the donut itself.
Cut the orange & yellow off of candy corns, where only the white tips remain, and use for toes & for tiny baby donut teeth
Use full size candy corn as teeth.
Make candy pumpkin 'hats' for your donut monsters.
stick in licorice strings for 'hair' or use pretzel sticks
Use pretzel sticks for arms