Thank you! I guess I shall stick to drinking pure water then :)
Forgot to mention -- water is the best thing you can drink.......
Diet sodas are not any better for you than regular sodas. Regular soda is full of sugar, which is bad for you. Diet sodas have artificial sweeteners which can make you crave sugar, even more.
I can't say you'll gain weight just from drinking the diet soda, but if makes you crave sweet or fatty foods, you might likely gain.