Wash the apples in warm water and then dry each one. This will remove the waxy coating on the apple and help the caramel stick. Using a folded dish towel, insert the sticks in the top of the apples, right where the stem is. Use the folded towel to push the stick as straight as you can down the entire center of the apple. Place prepped apples in the fridge.
In a medium-sized heavy-bottomed saucepan, add the water, sugar, corn syrup, and salt. Turn the heat to medium-high and stir constantly with a wooden spoon until the sugar is completely dissolved.
Once the mixture is boiling, stop stirring and watch closely until it turns an amber color. It may take about 10 minutes, but the change will happen fairly quickly. If it appears to be turning darker in one area much faster than the rest, gently swirl the whole pot. DON’T STIR IT! Stirring will cause the caramel to crystalize and it will become unusable.
Once it is a medium amber color, reduce the heat to medium-low and very carefully and slowly stir in the heavy cream. The mixture will bubble up and steam significantly. Continue stirring until the mixture reaches 246° and then remove from the heat. Stir in the vanilla.
Dip the apples in the hot caramel, swirling to evenly coat each one. Let the excess caramel drip off and then set the dipped apple on a piece of parchment sprayed with cooking spray or on a silicone baking mat sprayed with cooking spray. Allow cooling completely, about 30 minutes.
Once the apples are completely cooled if desired you can proceed to dip them in chocolate and then in the toppings of your choice.
