Preheat your oven to 350°F (175°C) and grease a muffin tin or line it with muffin liners.
In a large mixing bowl, combine the flour, sugar, baking soda, baking powder, salt, and cinnamon. Whisk until well combined.
In another bowl, whisk together the egg, milk, applesauce, and vegetable oil until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix!
Fold in the chopped apples, making sure they are evenly distributed throughout the batter.
Scoop the batter into the prepared muffin tins, filling each cup about ¾ full.
In a small bowl, mix the ¼ cup of sugar and 1 teaspoon of cinnamon together.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Remove from the oven, let cool for a few minutes, then roll warm muffins in the cinnamon-sugar mixture.
Enjoy warm with a cup of coffee or tea!