Apple cider vinegar is essentially just fermented juice, and the primary ingredient associated with its health benefits — acetic acid — is in all kinds of vinegar. If you do guzzle it down, research suggests it can help lower your blood sugar after a meal. And if you use it to rinse your hair, it might kill some of the microbes that make your hair stink and lead to dandruff. But nearly all other benefits you hear about, from curing yeast infections to whitening your teeth, aren’t supported by scientific research.