Kit Kats and Yorkie chocolate bars will see their sugar content cut by 10%, Nestle has announced.
The confectioner said it would use around 7,500 tonnes less sugar to make its products by next year.
The sugar will be replaced with higher quantities of other existing ingredients or other, non-artificial ingredients.
Products will also be kept below a certain amount of calories.
Fiona Kendrick, Chairman and CEO of Nestle UK and Ireland, said: "Our confectionery brands have been enjoyed in the UK for more than a century and we know that if we can improve these products nutritionally, provide more choice and information for the consumer, together with other categories, we can have a significant impact on public health"