Try something strong like (as suggested) vinegar or bleach. This might be a long shot but maybe drano. If it can push whatevers there to unclog a drain, presumably it would get rid of any smell at the same time.
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Try something strong like (as suggested) vinegar or bleach. This might be a long shot but maybe drano. If it can push whatevers there to unclog a drain, presumably it would get rid of any smell at the same time.