Sulfer What Is This Vinegar/Sulfer Smell In My Bathroom?

What is this Vinegar/Sulfer smell in my bathroom? - sulfer

I live with two other people on the third floor of an old house (think college apartment or a house, because that is what it is). We just clean the bathroom, even though none of it feels, detergents, cleaners and other bathroom smells good. This vinegar or Sulfer smell seems out of our range of office bath, may come under the carpet? But it's hard to say where it came from. It is very powerful, but does not feel good. Who knows what is or could be?