I've gotten the smell out of my plastic fermenters by soaking the crud loose with 3-4 TBSP of PBW in,then fill with water & stir. Let it soak 5-7 days,then use asoft cloth & my bottle brush to wipe the loose bit of crud that hasn't settled off. Then I place my home cheapo bucket on the floor beneath it (the FV's sit on my fermenter stand),& open the spigot to allow all to drain.
Then rinse it out good. Remove spigot & soak in a mug of PBW to loosen anything still in there. I take asoft cloth & starsan to clean the mounting hole area. I have a set of aquarium lift tube brushes to clean spigots & other small ID stuff. I scrub the seals & lock lugs too. Rinse all,then soak in starsan a couple minutes. Then reassemble to FV & starsan that,letting the starsan run back into the jug through the spigot. I sanitize again right before filling with chilled wort the next time. They look & smell clean at that point.