Prepare ahead

The toffee apples can be stored in a cool dry place for up to 2 days.

1. Push a wooden stick firmly into the stalk end of each apple.

2. Bring the demerara sugar, 1/3 cup water, butter, syrup, and vinegar to a boil in a heavy-bottomed, medium saucepan, stirring just until the sugar is dissolved. Attach a candy thermometer to the saucepan. Cook, without stirring, brushing down the crystals that form inside the pan with a pastry brush dipped in cold water, until the syrup reaches the soft-crack stage, 270-290°F (135-145°C).

3. Meanwhile, line a baking tray with wax paper and lightly grease the paper. Remove the pan from the heat. Dip an apple into the caramel to coat, tilting the pan if necessary, and stand the apple on the lined baking sheet. Working quickly, repeat with the remaining apples.

4. Let stand until the apples are completely cold and the toffee has hardened.