Cheerios are a great choice as far as cereal goes. there is a decent amount of fiber and they really do help reduce LDL cholesterol. Also there is hardly any sugar which is pretty rare to find in most cereals.
Primary ingredient is oats, and sugar is very low for a dry cereal (assuming you mean the original style plain ones, not the honey nut or other flavored ones which are high in sugar). One of the best dry cereals around, but still has a high glycemic index, which may not be desirable depending on the circumstances. If you want to eat oats but don't want to high glycemic index, plain oatmeal is a good choice.