Insert a wooden skewer or lolly stick into the stalk end of each apple. Line a large baking tray with baking parchment.
Put the sugar in a heavy-based pan with 120ml cold water and heat gently, stirring until it dissolves. Bring to the boil and add the vinegar, butter and golden syrup. Boil gently for 12 minutes, until it has reached the soft-crack stage (138°C on a sugar thermometer, or the point at which a little of the mixture, dropped into cold water, forms threads that bend slightly before breaking).
Dip the bottom two-thirds of the apple in the toffee, turning to coat. Working quickly, get the children to add sprinkles, stars or biscuit crumbs to each apple. Leave to set on the baking parchment for 15 minutes.