I am no expert, but my gut feel is that drinking vinegar or whatever other acid, natural or not, is going to severely acidify you! How much vinegar would you have to drink to get enough into your colon to kill off lets say Candida?
Vinegar will not get the live culture into your colon, where the "vinegar" culture can live and even prosper as long, as there is ethanol producing culture like Candida present. Once the ethanol culture more or less dies off, the vinegar culture will die off to.
Considering how fast can a "vinegar" culture kill vine, I would not be surprised if "vinegar" cells actually attached themselves to the "vine" cells like a baby to a teat and sucked them dry while killing them with vinegar. But that is a wild speculation :-)