Apple Cider vinegar is a vinegar made from fermented apple juice. Bacteria and yeasts in the apples produce alcohol from sugars, which is then converted to acetic and malic acids by another fermentation step involving “The Mother”, another bacterial organism. It is acidic, unpalatable and irritant in its concentrated form but harmless when diluted unless contaminated with additional yeasts and bacteria. In rabbits, any such bacterial contaminants are most likely to be killed by their acidic stomach content. If using this product, care should be taken that the taste of the water is not changed, leading to reluctance to drink it, and concentrated forms should be avoided, especially any capsule or tablet or other solid forms, which could irritate the mouth and oesophagus.
As to its possible health benefits, many are claimed, and few, if any, are proven, even in humans. The nutrient content of ACV is so negligible that it’s not a useful source of vitamins or minerals. Any “helpful” bacteria present are unlikely to survive the stomach acids. The acidic nature of the product is, likewise, not going to have any effect on the pH of the rabbit’s body or blood, or urine. If it conversely makes the water MORE palatable to an individual rabbit, this could be really helpful in diluting urine sediment and helping to reduce urine scalding.
In humans, there does appear to be some useful effect on blood sugar levels after eating (1). However, rabbits only very, very rarely develop diabetes, and their feeding strategy should involve ad-lib green leafy grass, hay and other plants rather than high carbohydrate foodstuffs, so it’s difficult to extrapolate from humans to rabbits.
In short, unless given in a concentrated liquid or solid form, and unless it put the rabbit off drinking adequate water, it shouldn’t do any harm. However, it’s equally unlikely to do any good, again, unless it encourages an individual rabbit to drink more.
- Shishehbor F, Mansoori A, Shirani F. Vinegar consumption can attenuate postprandial glucose and insulin responses; a systematic review and meta-analysis of clinical trials. Diabetes Res Clin Pract. 2017;127:1-9. doi:10.1016/j.diabres.2017.01.021