Place the apples in a large bowl, and then cover with boiling water. This will remove the waxy coating and help the caramel to stick. Dry thoroughly and twist off any stalks. Push a wooden skewer or lolly stick into the stalk end of each apple.
Have a sheet of baking parchment on a wire rack ready next to your stovetop. Tip the sugar into a pan along with the water and set over a medium heat. Cook for 5 minutes until the sugar dissolves, then stir in the golden syrup, Cinnamon and vinegar. Set a sugar thermometer into the pan and heat to 140°C or hard crack stage. If you dont have a thermometer you can test the toffee by pouring a little into a bowl of cold water. It should harden instantly and when removed be brittle and easy to break. If you can still squish the toffee, continue to boil it.
Working quick and carefully, dip and twist each apple in the hot toffee until covered, let any excess drip away, then place on the baking parchment to harden. You may have to heat the toffee a little if the temperature drops and it starts to feel thick. Leave the toffee to cool before eating. Toffee apples can be made up to 2 days in advance and stored in a dry place.