Take diabetic jam for example, little or zero sugar, but loaded with fat. If people bothered to read the sugar and salt content clock on most breakfast cereals they'd possibly think twice about buying them, the sugar content of things like Crunchy Nut Cornflakes doesn't bear thinking about, but...
Weetabix - loaded with sugar
Rice Krispies - loaded with sugar
Alpen (the one with sugar) - loaded with sugar
Corn Flakes - loaded with sugar
etc.
Shredded Wheat - the only 'mainstream' breakfast cereal outside of porridge with no added sugar (and bloody lovely it is too)