Mayonnaise isn’t exactly an exotic ingredient. In fact, Kewpie mayonnaise is something of a Japanese cultural icon. You would expect to find it on or inside of sandwiches and other foods typically taken to go.
Bananas are a fantastic on the go snack because they are self-portioned and give you plenty of sugar that your body can readily metabolize for continuing to walk around the city.
It's not that it's exotic. I just figure If I'm carrying sauce packets they are either sealed or opened and used. I'm not worried about any empty packets messing up my pockets significantly.