What could I use for smell coming from under sink. Have tried vinegar, soda, hot water, it goes away for a few moments, then returns, was previously a Dr's ofc, also connected to 4 other buildings in strip mall, everyone smells it..

My guess is that the plumbing is not properly vented and you are getting sewer gasses coming up from the sink. The solution is to have a plumber out to inspect and correct the problem. No amount of cleaning will correct this issue - there has to be a vent pipe to release the sewer gasses out of the building or they will back up into the building and you will experience this problem.

By under do you mean just inside the cabinet? Do any of the other 4 parts of the building have a similar issue?

Look to see if there is a mechanical vent under the sink (they usually have threads and can be unscrewed). If there is a mechanical vent it is probably detective and can be unscrewed and replaced.

Mark

If all those cleaning products did not help then your only solution is to got hrough an expert. Since there are four other businesses sharing this common problem, you should all chip in and resolve it immediately. I doubt any customers are happy to smell that.