Wash apples in hot water with baking soda to remove wax. Dry completely. Insert sturdy wooden sticks into the top of each apple.

Line a baking sheet heavily with parchment paper and lightly spray with non-stick cooking spray.

In a heavy-bottomed saucepan, combine sugar, water, and corn syrup. Stir gently off the heat to moisten the sugar.

Attach a candy thermometer to the side of the pan. Bring mixture to a boil over medium-high heat. Do NOT stir once it boils.

When temperature reaches 250°F (121°C), carefully add blue food coloring and edible glitter. Swirl the pan gently to mix.

Continue boiling without stirring until the temperature reaches exactly 300°F - 310°F (149°C - 154°C), known as the hard crack stage.

Immediately remove from heat. Stir in flavor extract if using.

Working quickly, dip each apple into the hot candy, twirling to coat completely. Let excess drip off for a few seconds.

Place coated apples on the prepared parchment paper. Allow to cool completely and harden at room temperature for at least 30 minutes before serving.