if that doesn't work (and it nearly always does) there is a product called Actizyme. It's a natural product without all the harsh stuff. It takes a couple of days but I find it much better long term than draino type stuff.
ETA sorry...should have refreshed before I started typing.
I've used bicarb and actizyme in the past (with drain blockages) and it worked ok, but for really persistant smells you can't go past vanilla fridge spray. It's basically alcohol plus vanilla and it works really well.
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