Much like its stinky cousin garlic, onions contain the amino acid allin. When cut, allin turns to propenyl sulfenic acid, which is thought to be the chemical responsible for the vegetable's eye-watering effects. It also is the chemical responsible for your mouth smelling like a rotting catcher's mitt.
2. Tuna sandwiches
The tuna sandwich is the absolute pinnacle of fishiness. It's the sandwich equivalent of a stink bomb. That sour, fishy smell occurs when seafood starts to oxidize, a common result of canning processes. Tuna packed in extra virgin olive oil is the least smelly, but regardless of how it's canned, something about that preservative-packed albacore seemingly permeates entire city blocks.