Some people drink apple cider vinegar for its perceived health benefits; however this is not recommended.
While it is theoretically safe to consume, apple cider vinegar is extremely acidic meaning it can erode tooth enamel and cause uncomfortable acid reflux.
If you do wish to drink apple cider vinegar, it is best to dilute it well, creating a more pleasant tasting apple cider vinegar drink that is a little more tooth-safe too.