Italian soda is a great low-calorie alternative to artifical-sweetener-ladened "diet" sodas. Soda water (sparkling, or club soda) + a pump or two of syrup.
If you're looking for non-soda alternatives, I agree iced tea and plain 'ole water is nice too.
Current program: 1,800 calories most days of the week; 45-60 minutes of mixed exercises (weights, cardio-kickbox, dance, athletic intervals) 6 days a week
Current goal: 135 pounds by birthday (July 14th) and to run half marathon at end of May.