Preheat your oven to 350°F (175°C).
Mix dry ingredients: In a bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon.
Combine wet ingredients: In another bowl, mix the diced apples, sugar, milk, oil (or applesauce), and vanilla.
Combine wet and dry ingredients: Add the wet mixture to the dry ingredients and gently fold until just combined.
Bake: Pour the batter into a greased 9×5-inch loaf pan. Bake for 50-60 minutes, or until a toothpick comes out clean.
Cool: Let the bread cool in the pan for 10 minutes before transferring to a wire rack. Allow it to cool completely before slicing.