Preheat your oven to 375°F (190°C). Line a muffin tin with paper liners.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and cinnamon.
In another bowl, beat the eggs, then add the oil and milk. Mix well.
Pour the wet ingredients into the dry ingredients and stir until just combined. Fold in the diced apples.
Divide the batter evenly among the muffin cups, filling each about ⅔ full.
Bake for 20 minutes or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.