Water.
Is there any particular reason you want to get your calories and nutrition in liquid form? If you actually do, there's a large variety of smoothies and such that you can make.
People "addicted" to soda are actually "addicted" to the sugar rush (usually enhanced by a bit of caffeine). Subject to all the usual caveats about people not being all the same, I don't think that a habit of regularly consuming a fair chunk of glucose and fructose in a rapidly-absorbed form is good for one's health.
yeah, everyone with a crappy diet gets told to drink water instead of soda, guess how often that actually works? In the interim of cutting down empty calorie intake, replacing those sources of sugar with milk, OJ, and bananas is much more practicable advice than drink water.
P/S/A: There are single sentences which can create life-changing amounts of difference.