Preheat to 400F. Generously grease a 24-cup mini muffin pan with nonstick spray. Set aside.
In large bowl, whisk together the apple cider, egg, and vanilla until combined.
Whisk in the brown sugar and 3 tablespoons melted butter until well-combined.
Add flour, baking powder, baking soda, salt, and apple pie spice.
Whisk in dry ingredients just until incorporated. Don't overmix.
Divide batter evenly between cups of muffin pans.
Bake for about 8-10 minutes.
While muffins are baking, whisk together granulated sugar and cinnamon in a shallow dish.
When the muffins are finished baking and are just cool enough to handle, dip tops of muffins in melted butter.
Roll muffins in cinnamon sugar mixture.
Let muffins cool to room temperature on wire cooling rack.
Notes
Brown sugar: Light or dark brown sugar will work in this recipe.
Butter: I use salted butter in this recipe. If you're using unsalted butter, add an extra pinch or two of salt.
Flour: To properly measure the flour, either weigh it or sift or stir it to break it up. Lightly spoon it into the measuring cup and level. Avoid packing the flour as packing the flour will give you dense or heavy donut holes.
Mixing: This is an easy, one-bowl muffin recipe. I recommend mixing it by hand to avoid overmixing the batter.
Cinnamon-sugar coating: For a heavier cinnamon-sugar coating, double that portion of the recipe.