Because it sweetens the grains, and adds taste, crunch, texture and color to the cereal. The amount of sugar in breakfast cereals is no more (and often less) than other common breakfast choices like fruit and yogurt, fruit juice, or toast with jam. Most breakfast cereals made with whole grain are rich in nutrients and can be a source of fiber and important vitamins and minerals. A 30g serving only accounts for around 8% of our total daily added sugar and energy intake.