Step 1: Line a baking sheet with parchment paper or a silicone baking mat and lightly grease it with non-stick spray. Remove stems from apples and firmly insert candy apple sticks or sturdy skewers into the core of each apple, about two-thirds of the way down, ensuring they are secure.
Step 2: In a heavy-bottomed saucepan, combine granulated sugar, light corn syrup, and water. Stir gently over medium heat until the sugar dissolves, avoiding stirring once dissolved to prevent crystallization.
Step 3: Increase heat to medium-high. Insert your candy thermometer and bring the mixture to a boil. Cook, without stirring, until the thermometer registers 300°F (149°C) to 310°F (154°C), reaching the hard-crack stage. This typically takes about 15-20 minutes.
Step 4: Once at the correct temperature, immediately remove the pan from the heat. Carefully stir in a generous amount of black gel food coloring until the syrup is uniformly black. Work quickly but safely, as the syrup is extremely hot.
Step 5: Working quickly and carefully, tilt the saucepan slightly to gather the syrup. Dip each apple into the hot black syrup, rotating it to fully coat. Allow any excess syrup to drip back into the pan, ensuring a smooth, even coating.
Step 6: Place each coated apple onto your prepared baking sheet. Allow them to cool completely at room temperature for about 30-60 minutes or longer in humid conditions. Resist refrigeration, as it can cause condensation and stickiness.