As Andree says you can run a trial run at 3-4 weeks out without issue if you do it correctly. That means not dropping water until Friday evening, limiting diuretic usage and not using loop diuretics or aldosterone blockers. You aren't going to gain an ounce of fat doing this because it shouldn't last longer than two days. A slong as you start drinking plenty of water saturday morning after judging your condition...you'll be back to normal in a day or two.
Again as Andre says its better to error on the conservative side...too many guys blow 16 weeks of dieting because they overload carbs thinking they are not full enough and loo watery and bloated....then you end up overdoing diuretics and you are in a push pull battle with the body...not good.
Quinine sulfate is used to stop cramping...it was more prevalent when loop diuretics were used such as lasix. You can use sugar free tonic water as an alternative as it is a natural form of quinine.
P