01 - Line a large baking sheet with parchment paper or a silicone mat. Insert a wooden stick firmly into the stem end of each apple, ensuring it's secure for dipping.
02 - In a heavy-bottomed saucepan over medium heat, combine granulated sugar, water, and light corn syrup. Stir continuously until the sugar completely dissolves and the mixture is clear.
03 - Increase heat to high and bring to a rolling boil without stirring. Attach a candy thermometer and cook until the syrup reaches 300°F. Remove from heat immediately when temperature is achieved.
04 - Stir in vanilla extract if desired. Quickly add several drops each of red, blue, and white gel food colorings. Gently swirl with a wooden skewer to create visible streaks—avoid fully mixing the colors.
05 - Hold an apple by the stick and dip into the hot candy syrup, turning to coat evenly. Lift and allow excess syrup to drip off, then place on the prepared baking sheet. Briefly swirl syrup between dips to maintain marbled pattern.
06 - Let apples cool at room temperature for approximately 15 minutes until the candy shell completely hardens. Do not refrigerate, as condensation can ruin the glossy finish.