Preheat the oven to 390°F (200°C). Line every alternate cup of a 12-cup muffin pan with muffin liners for tall, bakery-style muffins, or use a 6-cup muffin pan.
In a bowl, combine the milk (room temperature) and apple cider vinegar and let it sit for 10 minutes until slightly curdled.
Add the sugar, oil and vanilla extract to the milk mixture and whisk until the sugar is dissolved. Mix in the mashed banana until fully incorporated.
Add the flour, baking powder, baking soda, salt, and cinnamon, and stir until the batter is smooth and well combined.
Fold in the chocolate chips.
Fill each muffin liner to the rim with the batter, adding thick layer of crumble topping if desired. Bake for 12 minutes at 390°F (200°C), then reduce the temperature to 350°F (175°C) and bake for another 8–10 minutes.
Insert toothpick in the center if it comes out clean or witha few moist crumbs (not wet batter), they're done.
Let the muffins cool in the pan for 30 minutes before carefully removing and transferring them to a cooling rack to cool completely.
Store in airtight container for up to 3 days or freeze for 2months.