Preheat your oven to 170–175°C (fan) or 180°C (conventional). Grease or line a 9x5-inch loaf tin.
In a large bowl, mash the ripe bananas.
Add the brown sugar, eggs, oil, sour cream, vanilla, and coffee mixture. Whisk until well combined.
In a separate bowl, whisk together the flour, baking soda, baking powder, salt, and cinnamon (if using).
Add the dry ingredients to the wet mixture and gently fold using a spatula until just combined. Do not overmix.
Pour the batter into the prepared loaf tin. Top with banana slices or chopped chocolate, if using.
Bake for 50–60 minutes or until a toothpick inserted in the center comes out clean.
If the top browns too quickly, tent loosely with foil around the 40-minute mark.
Let the bread cool in the pan for 10 minutes before transferring to a wire rack to cool completely.