PLEASE KILL THE MYTH.
Soda causing dehydration is a myth that exists simply through repetition. It was said enough times that people believed it to be true with out any actually research.
Actual research does not support the myth that soda in anyway causes dehydration.
Current research says about caffeine.
# When consuming a caffeinated beverage, the body retains some of the fluid.
# Moderate caffeine consumption causes a mild diuresis very similar to that of water (water, when consumed in large volume, increases urine output).
# A person who regularly consumes caffeine has a higher tolerance to the diuretic effect.
Unless your downing caffeine pills, it won't cause dehydration.
2: Salt makes you more thirsty but does not necessarily dehydrate you. Salt attracts water so in small amounts in food can help hydrate you when taken with fluid. So eating some salty crackers with a glass of water can actually hydrate you more then simply drinking the glass of water alone.
Why does sea water dehydrate you then?
1 kg of seawater(or 1 liter) has approximately 35 grams of dissolved salts or 3,500 milligrams. (1g=1,000mg)
Humans can't drink salt water because the kidneys can only make urine that is less salty than salt water. Therefore, to get rid of all the excess salt taken in by drinking salt water, you have to urinate more water than you drank, so you die of dehydration.
1kg of coke (or half of 2-liter or 2.8 cans) contains 140 milligrams of Sodium. So salt water is 25 times MORE salty then coke.
Simply put there isn't enough salt in soda to counter the fluid intake. Its not as good as water but it won't dehydrate you. Soda does not dehydrate you but you have to drink more of it then you would is you just drank water.
I'm all for promoting good health but not at the expense of truth. When you repeat a lie through repetition(even unknowingly) everything else you say starts to sound suspect.