I managed 3 days. By the 3rd, my legs had become very heavy and my inertia was doubling up, my siesta now 3 long hours of complete absence. Falling alseep at night, my body horizontal and sleep once more my best friend, an image popped into my mind of a sun straddling a horizon line, in balance between above and below, and it seemed to me that it was representing something I was feeling. The urges in my body had mellowed, my desires had abated and I had rapidly lost a lot of those irritating impulses of "hunger" and "thirst". At 9pm, 20 minutres before we "broke", I had on each evening felt disinterested in the meal, and though we did gorge ourselves a lot in the 4 hour time window before bed, to the point of nausea in my case, this was more out of anxiety than anything else and a desire to stand up well to the next day and the 36 37Celsius heat.
So for 20 hours each day we had no drink or food, and also didnt use toothpaste or admit any flavourings to our mouth, as is correct muslim pratice. We had also shaved our arm pits and groin, as is also generally customary for a muslim. But by the 4th day, I became reluctant to continue, mainly because I am not a muslim and because the heat and an exhasuting one hour 5 a side football match sweated out an armful of body fluid and I had experienced what I ahd set out to.
It was really surprisingly easy, and if I was a believer it would have been no real challenge, but for comfort sake and also as I am trying to lose a little weight (ironically, though your stomach is shrunk by the fast, I was overindulging in the feast) I have since been mainly as normal, though I have done a couple of days of fast since. Try it, I think you will learn something from it, and as it is practiced between sunrise and sunfall, my memory of it will always be of that vision I had of the drowsy sun, balanced on the horizon line poised to set.