9 days Water Fast is my longest. I felt very tired, exhausted rather, during it. I believe I have mineral deficiencies which make that even more difficult.
I have done several 2 week fruit fasts though, and I am rather resistant to hunger in feeding time, meaning I can skip a meal and would be fine, but I hate doing it, because it affects my productivity.
Light food is best for me. I don't like dry stuff, and now would mostly opt for raw, but not dehydrated, if not - for soups and blends.
I will be trying for longer fasts.
I still think it is a good idea, but always listen to your body.