I forgot to mention that, in fact I had forgotten all about it. On the first three days of my 27 day fast I had whpping headaches due to caffeine withdrawal, but after that I was fine. When I re-introduced coffee last year, and started fasting (without coffee) I had no headaches.
On some of the later fasts I started drinking black coffee through boredom, but this resulted in me breaking the fast a few days later.
Same thing with lemon juice, I tried that as well. I know it's incredibly boring, but it is easier with water. The only cheat I got away with was using different water types. Probably that was more psychological than anything else.