Preheat oven to 350°F (175°C) and line muffin tin with cupcake liners.
In a bowl, mix cake mix, lemon-lime soda, and cotton candy flavoring until smooth.
Divide batter into two bowls. Tint one pink and the other blue.
Spoon both colored batters into each cupcake liner, filling about 2/3 full.
Bake 18–20 minutes or until a toothpick comes out clean. Cool completely.
In another bowl, beat softened butter until creamy. Gradually add powdered sugar.
Add heavy cream, vanilla, and cotton candy flavoring. Beat until fluffy.
Divide frosting in two bowls. Tint one pink and the other blue.
Fill a piping bag with both frostings side by side. Swirl onto cooled cupcakes.
Top with sprinkles and cotton candy just before serving.