I believe when we smell that sour "vomit" smell what we are picking up is acidic in some form or another. Why not try several boxes of baking soda and water, seal it in a plastic bag and set it in the sun. Shake whenever you remember to. Leave it for a week.
I don't remember if anyone asked but you have checked to see it isn't actual remains of someones urp, Right?
Best Wishes, Rob