Preheat oven to 350 degrees F. Spray 8 (4-inch) ramekins with butter flavored cooking spray and set aside.
In a bowl combine thawed blackberries, tapioca, lemon juice, 1/4 cup of cream soda and sugar. Transfer to ramekins.
In a large bowl combined biscuit mix and remaining cream soda. Mix until well blended. Sprinkle biscuit mix over berries. Dust with sugar. Bake for 30 to 40 minutes. Serve warm.