Preheat oven to 375°. In a large bowl, combine biscuit mix and 3/4 cup sugar. In a small bowl, combine eggs and sour cream; stir into the dry ingredients just until combined. Fold in blueberries.
Fill greased muffin cups three-fourths full. Sprinkle with remaining sugar. Bake until a toothpick inserted in muffin comes out clean, 20-25 minutes. Cool 5 minutes before removing from pan to a wire rack.