Dr. Oz says whether the twins drank water or not made no difference to their skin. The main reason for this, he says, is that food has water in it. "We get a lot of water already without having to go and get extra water," he says. "Now assuming you're not dehydrated—and neither of these sisters were—you won't have that problem."
Although Dr. Oz says drinking water doesn't matter to the skin, it does have other benefits. "Water's great to lose weight. It satisfies your satiety center. You don't get the urge to eat quite as much," he says. "It's got lots of benefits that go beyond its ability to affect your skin, but you don't have to force fluids to get that benefit."