The 
Environmental Working Group reviewed nearly 100 cereals and found many that are more than 50% sugar by weight (more than cakes and cookies) but are still marketed as children’s food.
A one-cup serving of [Kellog’s] Honey Smacks packs more sugar than a Hostess Twinkie…
Most children’s cereals fail to meet the federal government’s proposed voluntary guidelines for foods nutritious enough to be marketed to children. Sugar is the top problem, but many also contain too much sodium or fat or not enough whole grain.
Apparently not much has changed since 2008 when Consumer Reports reported basically the same thing; Kellog’s Honey Smacks had more sugar than donuts.
Are you one of those adults who keep a box of Frosted Flakes or Froot Loops hidden in the cupboard? Such sugary cereals are heavily marketed to children, to the tune of about $229 million advertising dollars per year. But an estimated 58 percent of “children’s” cereals are consumed by the over-18 crowd.
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The bad news is that 23 of the top 27 cereals marketed to children rated only Good or Fair for nutrition. There is at least as much sugar in a serving of Kellogg’s Honey Smacks and 10 other rated cereals as there is in a glazed doughnut from Dunkin’ Donuts.