Most store-bought jar sauce has sugar in it (and tastes gross). You can absolutely make sauce that doesn't have sugar in it, and some of the nicer jar sauces are that way also.
> or that fruit yogurt has more sugar than a Coke
Again, maybe if it's Dannon, but you can also buy plain yogurt and put fruit in it. Sweeten to taste.
> or that most breakfast cereals — even those made with whole grain — are 75 percent sugar
Maybe Post/General Mills sugar cereals, but again it's not that hard to find cereal with low sugar content.
This article argues that the problem is solved with regulation, but a lot of what we eat is influenced by government subsidy (i.e. corn/corn syrup), which makes many of the unhealthiest foods inexpensive. The article makes it sound like all processed food is loaded with sugar and that grocery shopping is dangerous. That may be true of "food deserts" but it isn't generally true.
The nutrition facts are already there. If somebody can't be bothered to see that whatever they are eating has 30g of sugar per serving, what can you really do about it?