Have you tried to rid your kitchen sink and maybe even your dishwasher of some random smell...
Sometimes is just stinks! I like this Liquid-Plumr product, you can buy it HERE. The sink stink was gone and it actually smelled clean for days.
In an effort to make sure nothin' else was causing the stink, I went ahead and gave the dishwasher a freshen up too. First, I removed the filter and cleaned it out, made sure nothing was caught in the trap, etc. Then, I ran it empty with this Lemi Shine product, you can buy it HERE. I LOVED this stuff and will buy it again and probably some other goodies they offer.
I actually went ahead and marked my calendar every 3 months to clean out the disposal and the dishwasher. Do you take time to clean these things on a regular basis?