Start by inserting a lollipop stick into the center of each apple, ensuring they are secure. Place the prepared apples onto a baking sheet lined with parchment paper and store them in the refrigerator to stay chilled while you make the caramel.
Secure a candy thermometer to the edge of a large, heavy-bottomed saucepan.
In the saucepan, combine the sugar, water, and salt. Set the pan over medium heat, whisking constantly until the sugar completely dissolves and the mixture reaches a vigorous boil. Once it boils, stop whisking.
Let the mixture continue to boil undisturbed until it turns a light golden hue, swirling the pan occasionally to check the color. Carefully and gradually pour in the chilled heavy cream, being mindful as it will bubble vigorously.
Lower the heat to medium-low and stir the mixture continuously with a heatproof spatula until it reaches 246°F on the thermometer. Remove the pan from the heat and stir in the vanilla extract.
Take the chilled apples and dip each one into the caramel, then return them to the parchment-lined baking sheet. If desired, roll the caramel-coated apples in your choice of toppings. Allow the caramel to fully set, which should take approximately 45 minutes. Afterward, you can add more garnishes or serve immediately. These caramel apples can be stored in the refrigerator for up to a week.