Most of it isn't, it will slow kill you and give you diseases. High fructose Corn Syrup and Aspertame are two of the most commonly known poisons that are in most soda. Also, the soda is made from fluoridated water, which is also a poison.
There is also rumors, or actual fact about aborted fetus cells being in popular sodas most people drink!
Just look at the people who have cases of diet soda in their carts at Walmart and tell me it's good for you. The proof is in the pudding.