Preheat the oven to 425 degrees Fahrenheit (218 degrees Celsius). Lightly spray or line one muffin tin, and set aside.
In a small glass measuring cup or bowl, whisk together the buttermilk, yogurt, egg, oil, brown sugar, and vanilla.
In a separate mixing bowl, whisk together the bran, flour, baking powder, baking soda, salt, and cinnamon. Gradually pour the wet ingredients into the bowl of dry ingredients, mixing just until combined.
Gently fold in the berries, dried fruit, or nuts into the bran mixture.
Scoop the batter into the prepared pan, dividing it evenly between the wells. Place in the oven and bake for 14-16 minutes or until the tops are golden brown and spring back when touched.
Remove from the oven and allow to cool in the pans for 5 minutes before transferring to a wire rack to cool completely.