Soda is a bit addictive. The caffeine and sugar, if you drink the ones with sugar. The caffeine isn't nearly as high as coffee, but if you drink tons then it will disturb your sleep patterns and I even believe dreams. (Before I got diagnosed with anything, I was drinking sugary soda and coffee instead of my usual water and I ended up with this nightmare disorder nonsense. I'm still way addicted to that stuff and hence am typing this up at 12:30am!)

And be aware - diet things can cause strokes and high blood pressure if you drink them a lot!