Does any one know of any substance (drugs) that smells?

Drugs that smell like a bad drain or sulpher or something like that? There is this smell from a neighbours on occasions that is making me feel sick. The man there is pleasant sometimes but on the occations I detect this smell his mood changing. He becomes loud, aggresive and violent. It appears to me that he could be taking some kind of substance and it coinsides with this really over powering smell.

Does anyone know if any drugs smell like that? it even smells like gas or bad eggs.