Wash the apples thoroughly. Insert the sticks and set aside on baking paper.
In a large saucepan, melt the sugar and water until all of the sugar granules are completely melted.
Cook for another 5 minutes on medium heat. Using a candy thermometer, cook until the sugar has reached a temperature of 140°C.
Add the vinegar, food colouring and golden syrup, and stir to combine.
Remove the toffee from the heat and let it stand for about 30 seconds until it stops bubbling. Carefully dip each apple in the toffee and place on the baking paper to set.