I think chronic fatigue is associated with viruses, I seem to remember Epstein Bar virus's get a lot of mentions on the subject. So it would seem any diet that keeps your immune system chugging is good.
If the virus hypothesis bares much scrutiny, then focusing on things that beef up your immune system seems logical. Good nutrition paying attention to Vitamin D/A status, zinc, and (cautiously) iodine.
You might persuade be able to persuade a good doctor help with antivirals possibly. Ideally you want a good doctor .
Not sure about the coffee thing, I love coffee but I'm pretty sure if I tried to drink 50 cups of it in one day I'd be able to levitate off the ground on a gusher of my own vomit, which would fulfill my dreams of flying under my own power but is probably exhausting in its own right.