Mahdi Yusuf's "Fasting & Programming" describes programming during Ramadan:
I have to say it is incredible how worse off you are when you aren't able to eat (or drink) and trying to do work that is involved. For example today I was in some code that I wrote literally a little over a month ago without difficultly and for the life of me I was unable to write something very similar without doing it over 6 times.
Mahdi talks about how hard coding during Ramadan is, and what he has learned from it. Perhaps my favorite nugget was "5 good hours are better than 10 bad ones."