Preheat oven to 425 degrees. Lightly spray a 12-hole mini muffin pan with cooking spray and set aside.
In a large bowl, use a hand-held mixer to blend together the milk, sour cream, eggs, and maple syrup.
Next, beat in the butter and vegetable oil.
Add the flour, baking powder, baking soda, sugar, and cinnamon. Beat into the wet ingredients.
Using a small cookie scoop, portion about 1 1/2 teaspoons of muffin batter into each muffin cavity in the mini muffin tin.
Bake for 10 minutes. Remove from oven and transfer to a wire cooling rack to cool. (Depending on how many mini muffin tins you have, you will need to bake in batches.)
When the mini muffins have fully cooled, whisk together the confectioner's sugar, maple syrup, milk, and cinnamon until the icing is smooth and consistent. For a thicker icing, add more confectioner's sugar. For a thinner icing, add about 1/2 teaspoon of milk at a time.
Dip the mini muffin, top side down, into the icing. Lightly shake the excess icing off and place onto a wire cooling rack with a baking sheet under it.
Sprinkle the tops of the mini muffins with sprinkles and allow the icing to harden before serving.
Once the icing is hard, pack mini muffins in a resealable container with a tight-fitting lid to keep fresh.