Soak the apples in a mixture of hot water and a few tablespoons of vinegar for 10-15 minutes. Brush the apples with a clean brush to help remove the wax. Rinse thoroughly, then wipe them dry. Clean the apples with a cloth dipped in vodka to remove any remaining residue, leaving the apples extra clean for dipping.
Put your apples near the stove so they’re close by when you need them. Also, prepare a cookie sheet with parchment to keep close.
Mix the sugar, water, and corn syrup in a medium saucepan. Attach the candy thermometer to the side of the pot, but make sure it’s not touching the bottom of the pan. Heat over medium-high heat and let bubble without mixing until it reaches 300 degrees.
Once it reaches that temperature, immediately take off the heat with a heat-proof rubber spatula.
Mix in the vanilla extract and the white food coloring until combined.
Quickly add a few drops of the two other colors.
Use a wooden skewer to gently stir the colors, but don’t mix.
Lightly move the colors around. Tip the pot to one side and dip the apple in the candy, coating it on all sides.
When you pull the marbled candy apple out of the sugar, give it a second to drip off the bottom, then place it on the parchment paper to cool and harden.