Put the sugar in a saucepan and add the corn syrup and salt. Give it a nice stir. Put on the stove over medium-high heat. The sugar will dissolve, get nice and clear, and then start bubbling and turn a golden brown.
Meanwhile, poke a chopstick through the center of each apple.
Once the caramel is nice and brown, stir in the butter. Turn off the heat. Add the cream, but be really careful because it releases a lot of steam. (I wear an oven mitt to stir.) Then add the vanilla and mix in. Have a bowl of ice and water, and put a metal bowl on top. Scrape the caramel into the metal bowl. Let the caramel cool a bit in the ice bath.
Dip the apple in the bowl, coating with the caramel. Use a rubber spatula to help the process, if needed. Then dip the coated apples into the toppings of your choice, place on a plate and let harden up a bit.