Preheat your oven to 350°F (175°C) and line a cupcake pan with cupcake liners.
In a large bowl, mix the white cake mix, Grape Crush soda, vegetable oil, egg whites, vanilla extract, and food coloring (optional). Whisk until smooth.
Spoon the batter evenly into the cupcake liners, filling each about 2/3 full.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Let the cupcakes cool completely on a wire rack.
Beat the softened butter until creamy. Gradually add powdered sugar, then stir in Grape Crush soda, vanilla extract, and food coloring (optional). Beat until fluffy.
Once the cupcakes are cool, frost them generously with the grape frosting.