Drinking just plain water can be kind of boring and one is tempted to drink fruit juice or even soda pop instead; thus ingesting too much sugar. One good thing about saunas is that one can get somewhat dehydrated and then just plain water tastes pretty good.
Saunas give regular tap water more of an appeal and make it easier for me to drink more water. I don't go for real hot saunas, however. I go in for a fairly short period and then go back and forth as it's more of a social time for me at the YMCA than anything else.
As for body cleansing properties, I don't know if it's that big a deal, but it does make me work up a thirst that can be quenched by nice cool water. I'm getting into the habit of drinking water more and fruit juice less. A good way to cut down of sugar since most Americans have way too much sugar in the diet.
Dancing is another good way to work up a thirst. There's one dance here in Bellingham entitled "Sweat Your Prayers."
Soda pop, that's even worse than fruit juice. I don't drink that very often. I use Stevia to sweeten my chocolate milk rather than the regular chocolate syrup they use in commercial chocolate milk.
I drink some fruit juice and even a small glass of soda pop once in a while.
There was an interview on Diane Rhems about too much sugar in American diets. They talked about crushing 6 oranges into a glass of juice versus eating 6 oranges. One gets the sugar of 6 oranges from the glass of juice, but one wouldn't normally eat that many oranges in once sitting if they were eating the oranges as oranges. Maybe better to just eat one or two oranges and then drink water. Less sugar and more fiber.
My blood sugar level is still pretty tame compared to the average American.