One obvious way is to cook everything yourself from raw ingredients. But of course that's less convenient than using processed and prepared foods.
I'd suspect plain Bran flakes or Shredded wheat will have added sugar.
edit:
Kellog's Bran Flakes
Wholewheat, Wheatbran (21%), Sugar, Barley Malt Flavouring, Salt, Honey. Niacin, Iron, Vitamin B6, Vitamin B2 (Riboflavin), Vitamin B1(Thiamin), Folic Acid, Vitamin D, Vitamin B12.
Sugar is the third ingredient, more than salt. And that's a non-sugary food.