Is not drinking water for a day or two really not good? what are its side effects? both inside and out. thank you very much :)

Not good.: Body needs water to carry out basic physiologic processes and excrete waste. Kidneys must excrete about 1 liters per day in the average human. If you do not replace this ( and a little extra) you will become progressively dehydrated developing constipation, cotton mouth, headache and disorientation. If this is prolonged you will develop irreversible kidney failure.