I usually drink a TON of soda (and not diet either. I can't stand that awful taste). I've dropped to a can or two a day, and I've been doing a week on, then a week off of eating vegetarian. I haven't added any exercise yet and I've already lost over ten pounds.
You can lose weight drinking soda, but it's unhealthy for you for other reasons.
Imagine how much I'll be losing when I actually start exercising!