Because someone drinking water is extremely different and should be reacted badly to... lol
But uh, how much coke do you normally consume? If you just drink an average of one can a day, just try drinking water for one whole month straight and see if you still have these symptoms at all. I mean I'm no doctor and I have no idea what's going on, but could be diabetes issues, could be pancreas not processing sugar well, could be liver not processing coke well, who knows? A good flush with just water through your system might do it a world of good.