Preheat the oven to 450F. In a large mixing bowl, combine the Bisquick and sour cream (the mixture will be crumbly). Add the Sprite and stir until the dough forms.
Coat the bottom of a 9x13-inch glass baking dish with about 1/3 of the butter. Scoop the biscuit dough into the buttered baking dish, pour another 1/3 of the melted butter over top of the dough. Use a spatula to spread the dough out evenly edge to edge in the baking dish.
Use a knife to cut the biscuit dough into 12 square biscuits. Drizzle the remaining butter all over the top of the biscuits.
Bake the biscuits at 450F for 15 minutes, or until golden brown on top. Remove the biscuits from the oven, set on cooling rack and cool for 5 minutes before brushing a bit more melted butter over the top, cutting and serving.