Coconut water is said to have been used as an intravenous drip in the wars, when they were out of the potassium-sodium mix.
It is completely sterile, so in practice they could transfer it right in from the nut.
If it brings more liquid to clean your bowels, I dont know.
Been in Asia a few times, coconut water fresh from the nut is a big favorite of mine, and I hardly ever had problems down there as long as having a nut or two a day.