As @Ripshod says ACV is not of much, if any, use. You will want to give probiotics for awhile. Antibiotics are not selective and kill the natural flora and fauna in the digestive system as well as the bad microbes. Probiotics replace these natural flora and fauna that assist in digestion. ACV is nothing more than something a little acidic.
I have heard of ACV being given after a round of antibiotics. Apple Cider Vinegar has antibacterial, antiviral, and anti-fungal properties. Man has been using it for thousands of years. But it is very important that it only be used for short-term use because it not only kills the bad bacteria, but also the good. I would advise you check with your vet - if he suggests it, you need to find out how much to give and how long for.