Pop the popcorn kernels using your preferred method (air popper, stovetop, or microwave). Ensure there are no unpopped kernels. Place the popped popcorn in a large mixing bowl.
In a medium saucepan over medium heat, combine sugar, butter, corn syrup, and salt. Stir continuously until the mixture comes to a boil.
Once boiling, stop stirring and let the mixture cook for 4-5 minutes. It should reach a temperature of 235°F (soft-ball stage). If you don't have a candy thermometer, you can test a small amount in cold water – it should form a soft ball.
Remove the saucepan from heat and quickly stir in the baking soda, vanilla extract, cotton candy flavoring, and food coloring (if using). Mix until well combined.
Pour the candy coating over the popped popcorn. Use a spatula to gently fold and coat the popcorn evenly with the candy mixture.
Allow the coated popcorn to cool for a few minutes, making sure it's cool enough to handle. Break the popcorn into clusters or individual pieces.
If desired, garnish with cotton candy for an extra touch of sweetness and a pop of color.