Preheat the oven to 350 degrees.
Wash and remove the core of the apples. Dice them into small pieces.
In a large bowl, add all the dry ingredients: flour, baking powder, baking soda, salt, cinnamon, and brown sugar (optional).
In another medium bowl, add and mix all the wet ingredients: applesauce, vanilla, vinegar, and plant-based milk. Whisk and mix all of them.
Pour the wet mixture into the dry ingredients in the large bowl and whisk until all ingredients are combined. Add the diced apples and mix again. Let it sit for 10 minutes.
Take a muffin tray and line with the muffin liners. Use a spoon or ice cream scoop to pour the mixture into the tray one by one.
Place the muffin pan in the oven and bake for 25 minutes at 350 degrees. Test the doneness by inserting a toothpick.
Remove from oven when done and let the muffins cool before serving.