The easy way to determine the sugar in foods is the nutrition label. Carbs are sugar, or close enough. I'll try the cherry extract. Worth a shot.

“For example the ONLY low sugar cereal you will find in a grocery store is Corn Chex or Rice Chex”

Also:
Shredded Wheat
Cheerios
Grape Nuts (not the flakes)
Uncle Sam (if you can find it)

^^^^^
And, for the second time, old fashioned rolled oats.
Cereal? Check.
No added sugar? Check.
Available in most grocery stores? Check.

Very nutritious and moderately priced to boot.