Every single one, every single time. The most common response has been "the yeast in the bread"
Debunk: Breads from other sub shops contain yeast and don't smell like ass ass.
The smell is so godawful that I can't for the life of me comprehend how people can have a meal in there. Seriously, it's like eating in a barn. I've only noticed this putrid, rank ass stench at Subway.
Mr. Sub, Quiznos, and my old favorite Blimpies are all immune. What's the goddamn deal here?