Prepare the Apples:
Wash and thoroughly dry the apples, removing any wax coating. Insert the wooden sticks into the top of each apple, making sure they’re secure. Line a baking sheet with parchment paper or a silicone baking mat and set aside.

Make the Candy Coating:
In a medium-sized saucepan, combine the granulated sugar, corn syrup, and water. Stir over medium heat until the sugar dissolves and the mixture comes to a simmer. Use a candy thermometer to monitor the temperature.

Cook the Candy:
Once the mixture begins to simmer, allow it to cook without stirring until the candy thermometer reads 300°F (150°C), which is the hard crack stage. At this point, remove the pan from heat.

Flavor and Color the Candy:
Stir in the vanilla extract and citric acid (if using). Then, divide the candy mixture into two bowls, one for each color of the cotton candy swirl. Add a few drops of blue food coloring to one bowl and pink food coloring to the other, stirring gently to combine. You should now have two bowls of brightly colored candy coating.

Dip the Apples:
Hold each apple by the stick and dip it into the first color of candy coating, ensuring that the apple is fully coated. Lift the apple out of the coating and allow any excess candy to drip off. Immediately dip the apple into the second color, gently swirling the apple to create a cotton candy swirl effect. If you want a more pronounced swirl, you can alternate dipping the apple into the two colors to build up layers.

Set the Candy Apples:
Place the coated apples on the prepared baking sheet. Let the candy apples cool and harden for about 15-20 minutes at room temperature. If you want them to cool faster, you can place them in the fridge for about 10-15 minutes.

Serve:
Once the candy coating has set and hardened, the cotton candy swirl candy apples are ready to serve! Enjoy the sweet, colorful treat with family and friends!