There are different types of sugars, such as lactose (milk sugar), fructose (fruit sugar) and sucrose (granulated sugar). Sugars are often added to foods because of the sweet taste, but sugar has multiple other functional properties. For example, it is a shelf-life extender and can be used as a bulking agent. But it can also be added in small quantities as a substrate for yeast in bread (to cause it to rise) and fermentation processes. In meat products, small quantities of sugars can be added to serve as carrier molecule for aromas and flavouring components.
Like other carbohydrates and proteins, all types of sugar provide 4 kcal per gram. By comparison, alcohol provides 7 kcal per gram and fat 9 kcal per gram.