The cheers program does cover sodas, but the soda program does not include bottled water, so you may want to buy a case of H20, which is 12 bottles for $ 2.99. You can get a glass of water, coffee, tea, or juice almost any time on the Lido deck, with or without the soda program.
We've cruised both with and without the cheers program, and it was about a break even for us. Consider that everyone in your cabin must purchase the program, that it will cost $ 57.44 per day with gratuity (include the day you board, but not the day you disembark), and you may be ashore for good portions of your cruise. If you're a wine drinker, each person can bring a bottle on board, and there are wine packages that are more cost effective if that is your beverage of choice. That, plus some of us can't drink on consecutive days like we used to back in college.
Cruisin has a chart that shows you the break even point for the cheers program. Basically, if you'll buy more than seven cocktails or nine beers per person, per day, you can save some money. It is handy- very handy IMO, to have your drinks on a fixed cost and not have to worry about it.