How do monks live with medical conditions that require regular meals? Theravada monks are supposed to eat only one or two meals per day, only between dawn and noon. For the rest of the day, they can drink water or fruit juices. The exception to this rule is if they are temporarily ill.

But what about monks who have Gastroesophageal Reflux Disease (GERD) or other chronic diseases, who may need to eat regularly every 4 hours or so, till usual dinner time?

Furthermore, people with GERD may not be able to consume acidic drinks (e.g. citrus fruit juices and tomato juice), especially on an empty stomach.

Also, consider that according to this article, up to 28% of Americans and up to 26% of Europeans, may be suffering from GERD. So, theoretically, this could affect 1 out of 4 monks.

How do they cope with this condition? Are they permanently exempted from this rule?
How do they cope with this condition? 


By following a doctor's recommendation, presumably. 

For arguments sake, we could apply a relativistic approach to the meaning of "coping". Buddhist practice can be and is a valid coping strategy in certain medical conditions, provided that a medical paradigm has ran out of answers (A strictly hypothetical example: certain conditions of chronic pain).


  Are they permanently exempted from this rule?


One way to look at this is that buddhism is about making people function/feel better for the sake of themselves and their surrounding. If a dogmatic adherence to religious principles worsen a persons health, then it can't be considered kusala. 

The exempt is likely permanent for as long as health conditions remains permanent. So, if conditions changes, perhaps a new take on buddhist practice could be relevant.