01 - Preheat the oven to 375°F. Line a 12-cup muffin tin with paper liners or lightly grease the cups.
02 - In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and ground cinnamon until evenly mixed.
03 - In a separate bowl, whisk the eggs, vegetable oil, whole milk, and vanilla extract until fully blended.
04 - Pour the wet ingredients into the dry ingredients and gently stir until just combined, avoiding overmixing.
05 - Fold the diced apples carefully into the batter to distribute evenly.
06 - Divide the batter evenly among the muffin cups, filling each about three-quarters full.
07 - Combine the sugar and cinnamon in a small bowl, then sprinkle the mixture generously over each muffin.
08 - Bake for 18 to 22 minutes, until a toothpick inserted in the center comes out clean.
09 - Let muffins cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.