I'm surprised nobody has said much about diet sodas here. Are artificial sweeteners too much of a controversial subject?
I feel the same about most beverages besides water (I'm still on the fence about milk, but I suppose unsweetened soymilk and the like are acceptable to me, too). They are treats. There's nothing you can get from any drink that you can't get from other, healthier sources (including enjoyment, but that's a whole other conversation). Like all other treats, they should be used in moderation. They shouldn't be a substitution for anything else, fruit, water, or otherwise.
That said, I do understand that they can be very useful in medical emergencies. As mentioned before by goodweed, juice is one of the quickest ways to replenish dangerously low blood sugar caused by diabetic emergencies, over-exertion, etc. It was certainly indispensable at blood drives in high school! Sports drinks can be helpful during and after prolonged physical activity, and even chocolate milk can make a reasonable recovery drink.
I have a bottle of juice in my pantry (along with some cookies, a cake mix or two, and even a few boxes of mac n cheese), and occasionally I have a few sips of soda or lemonade at work, but I recognize that these are not the healthiest choices I make during my day. I think it just becomes too much of a habit for many people, including myself at some points in my life, and that's without adding addictive caffeine into the mix.