What is the ruling on drinking barley beer prescribed by a doctor for treatment, knowing that it contains a very small percentage of alcohol that cannot be removed?

If the physician advises drinking alcohol-free barley juice, the patient can prepare it themselves to ensure it is free from intoxicants. If this is not possible, and the patient cannot find any other treatment, and the physician informs them that drinking it as is is necessary for the patient's health, then there is no objection to consuming it out of necessity, provided that the necessity is proportioned to its extent. The treatment should be discontinued when it is no longer needed due to recovery or the availability of a permissible alternative.