Combine the baking mix, sour cream, and 7-up in a bowl and mix until a dough forms. Drop onto baking sheet. For a more uniform shape, turn the dough out onto a lightly floured work surface. Roll out the dough with a rolling pin and then cut with a biscuit cutter.
Dip the biscuits in the melted butter, letting any excess drip off. Place the biscuits on a rimmed baking sheet. Drizzle the remaining butter over the top of the biscuits.
Place the baking sheet in the oven and bake at 425 degrees F for 15 minutes or until the biscuits are cooked.