Drinking water in the morning overcoming the lack of fluids during sleep
Very reasonable if when you wake up and then feel thirsty. Not only do you feel thirsty, but the cells in the body feel the same way. This is because during the night you 'fast' so that the body is not well hydrated.
Drinking water while waking up reduces the risk of dehydration
Many people often ignore the thirst and do not directly drink water to overcome it. Of course this increases the risk of dehydration. The dehydrated body will slowly experience impaired kidney function, various heart diseases, low blood pressure, even seizures.