Preheat the oven to 400ºF or 200ºC and line a standard muffin tin with 12-15 paper liners.
Mix the plant milk and vinegar in a jar or bowl until well combined. Let the mixture rest at room temperature for at least 5 minutes. After this time, the milk will thicken and curdle.
In the meantime, add the dry ingredients to a large mixing bowl (flour, sugar, baking soda, baking powder, cinnamon, and salt) and mix until well combined.
Add the mashed bananas, oil, vanilla extract, and the plant milk and vinegar mixture. Stir until well combined.
Add the vegan chocolate chips and stir again until well combined. Omit this step if you don’t want to add the chocolate chips.
Spoon the batter into liners, filling them all the way to the top.
Bake for 20 to 30 minutes or until golden brown and a toothpick comes out clean.
Remove from the oven and let them cool completely on a cooling rack.
Serve your vegan banana muffins immediately.
Keep the leftovers in an airtight container at room temperature for up to 5 days. You can also freeze the muffins for up to 2 months. To thaw, just pull the muffins from the freezer and let them thaw at room temperature for several hours.