Adjust an oven rack to the middle position. Preheat oven to 400°F. Line a standard 12-cup muffin tin with paper liners or grease well. Take about half of the All-Bran cereal, place it in a food processor, and process until finely ground. Alternatively, place half of the cereal in a large zip-top bag and use a rolling pin or meat mallet to crush it into fine crumbs. Set aside.
In a large bowl, whisk together the flour, baking soda, and salt.
In a separate bowl, whisk together the sour cream, oil, eggs, brown sugar, molasses, and vanilla extract.
Stir in the crushed cereal and the remaining whole cereal. Let the mixture sit until the cereal is evenly moistened, about 5 minutes.
Add the wet ingredients to the dry ingredients. Stir just until combined; do not over-mix.
Gently fold in the raisins, cranberries, or cherries (if using).
Divide the batter into the prepared muffin cups, filling each cup to the top.
Bake for 16 to 20 minutes, or until a toothpick inserted in the center of a muffin comes out clean.
Cool muffins in the pan for about 5 minutes, then transfer to a wire rack to cool completely.