Wash and dry firm apples thoroughly
Remove stems and insert sticks into the tops
Line a baking sheet with parchment paper or a silicone mat
Combine sugar, corn syrup, water, and food coloring in a saucepan
Heat the mixture over medium-high heat until it reaches hard-crack stage
Remove from heat and stir in flavoring if desired
Tilt the pan and dip each apple into the candy coating
Rotate the apple to coat it evenly
Let excess coating drip off
Place coated apples on the prepared baking sheet
Allow the candy shell to harden completely before serving