Preheat oven to 350°F. Spray doughnut baking pans with non-stick cooking spray and set aside.
In a large bowl whisk together cake mix, egg, water, cream, and vegetable oil until smooth. Pour mixture into a large resealable bag.
Cut a small corner of the bag and pipe the batter into the baking pan filling each doughnut two thirds full.
Bake for 12-14 minutes or until the edges just start to brown. Let doughnuts cool in the pan for 15-20 minutes, then remove from pan.
Allow doughnuts to cool completely before glazing them. To prepare the glaze, whisk together powdered sugar, butter, and cream until smooth. (If desired, divide glaze into two bowls. Color one with a few drops of red food coloring and the other with a few drops of green food coloring. Stir to combine.) Dip doughnuts into the glaze, then decorate with sprinkles. Let the glaze set before serving.
Doughnuts are best when they are fresh but you can store them in an airtight container in the refrigerator for up to 3 days. Let them come to room temperature before serving.