Apple cider vinegar, along with other types of vinegar,Â goes bad after around 5 years. It stays good indefinitely if it is unopened.
Apple cider vinegar has highly acidic properties which helps it remain good, even after long periods of time. Vinegar is often used as a preservative in other foods to help extend their shelf life. If the vinegar has other ingredients added, it can cause the liquid as a whole to go bad. In these instances, the bottle typically has an expiration date printed on it. This is the "best-by" date, and it can be used for several months after the date passes.