Suspect foods – read the labels.
Many condiments and sauces are filled with sweeteners. This includes ketchup, barbecue sauce, teriyaki sauce, mayonnaise (varying by brand), tartar sauce, and many others.
The most widely-sold brands of peanut butter add considerable amounts of sweeteners (most “natural” brands do not).
Widely-sold brands of pasta sauce often contain several teaspoons-worth of sugar per jar.
Bottled salad dressings are often surprisingly sweet.
Many processed meats and bacons contain sweetening.
Most ready-to-eat breakfast cereals are significantly sweetened.
Bread and rolls, in fact, all bread products, run the risk of sweetening.
The bottom line: nearly any prepared food product can have significant sweetening. Read both the ingredients list and the nutritional table.