Wash and thoroughly dry the apples, then insert a candy apple stick into the stem end of each apple.

Combine sugar, corn syrup, and water in a heavy-bottomed saucepan over medium heat, stirring until the sugar dissolves.

Bring the mixture to a boil without stirring, and continue to cook until it reaches 300-310°F (149-154°C) on a candy thermometer (hard crack stage).

Remove the saucepan from heat and carefully stir in the red food coloring.

Dip each apple into the hot candy mixture, turning to coat completely, then place them on a greased baking sheet or parchment paper to cool and harden.