Wash and thoroughly dry the Granny Smith apples. Insert a stick into the stem end and line a baking sheet with parchment paper.

In a medium saucepan, combine granulated sugar, corn syrup, and water. Heat over medium, stirring until boiling. Use a thermometer to check it reaches 300°F (hard crack stage), about 10-15 minutes.

Remove from heat and add food coloring if desired. Stir until evenly distributed.

Dip each apple into the hot mixture, swirling to coat. Let excess drip back into the pan.

Sprinkle edible glitter over the wet coating while still soft for best adhesion.

Allow the apples to cool at room temperature for about 30 minutes. Store in a cool, dry place once hardened.