If you have one cup of skim milk with your oatmeal, assuming the oatmeal has absolutely no sugar at all (which isn't the case), you'd be having 13 g of sugar. I usually like to mix in a spoonful of brown sugar with my oatmeal, adding another 5 g of sugar. Maybe you don't do that; everyone's different. Putting in half a banana would add 7 g of sugar.

A packet of Quaker cinnamon flavour instant oats has 10 g of sugar. If you have two packets, it is roughly equivalent to making regular oatmeal with half a banana (7 g), a spoonful of brown sugar (5 g), a tablespoon of peanut butter (1 g) and half a cup of milk (6 g)

Granted, the combination of making it yourself is a lot more nutritionally whole, but if we're just comparing sugar content, it's actually not that bad.

I found the nutritional label, which reports 10 grams of sugar per packet. That, to me, is reasonable. I did not look up the nutritional information of the cereal, but remember that sugar content isn't the whole story. The cereal is more or less deficient in nutrients whereas oatmeal isn't. Oatmeal is a complex carbohydrate.

As another example, if you had a banana and whole oats, no sugar, that meal would be obviously very healthy but nominally have 15 g of sugar.