Wrinkle your noses.
OK, this one might be a little icky. But what is your least favorite food smell?
Mine is tuna fish. I know, not surprising the vegetarian doesn’t like a meat smell. But I can usually handle others. Some even smell good, despite having no desire to eat them.
But the smell of a tuna fish sandwich, especially somewhere contained like a train or classroom, makes my insides want to curl up and die.