Good Heavens. I have just moved into a new luxury apartment. The second day of the move a furious odor that is best described as rotten cabbage filled the apartment. There was no food yet present, no cooking had taken place.
Eight plumbers, including but not limited to the builder of this building have been to the unit and are completely perplex. Naturally, I am "the only person this is happening to." The next morning, the odor was completely gone. A week later it returned. It lasted a day. Two weeks went by. The odor has returned and now has been a constant sickening stench for five days. There is no odor coming from any of the drains. I have got to believe something has died. This is a very urban area and it really does not smell like decomposition.
I have no choice but to move. I will always wonder what this is. Your thoughts?

First, have you talked to other residents in the building? The management sounds attentive, but might not be telling you if others have the smell too. I'd knock on doors and leave notes.
Second I would tell the landlord that you will be calling the Health Dept and Building Inspector within a day, and then do so. I assume you haven't stopped letting him know what is happening. Being perplexed is one thing but just letting it go at that makes no sense.
Close all doors in the apartment rooms. Try to determine if any closed rooms do or do not smell.
Get affidavits from people in case you sue for moving costs or even staying cost.

Foods, sewage, and decomposing animals each have a different smell, although all share some gasses, notably sulfides. A dead animal develops a worse and worse stench that is indescribable, even one dead mouse. I think part of that is methane and ammonia.
Then there's the venting of plumbing. It's possible a vent pipe has become unattached inside a wall or under a floor/ceiling. That's for the builder to determine. Ask if any kind of renovations have been done recently. See if you can find out who the previous tenant was and why they moved out.

Excellent post by joypulv. Before you can began a repair you must localize the source of the odor. Is it worse in one room or section of the unit? Any part of the day or night when the smell's the strongest? Going along with Puff on the open vent in the wall thing. A smoke test would settle that issue. Puffs advice to bring the health Department in is right on. That smell just has to be unhealthy. Good luck and keep us informed. Tom