If you haven't cut out soda, it's a good idea. Soda (IMO diet or regular) is just horrible for you. If you are hardcore like Tony Horton (I've read his book and done P90X), you will stay away from artificial sweeteners (Sweet & Low, Splenda) too. They say that artificial sweeteners can make your body *think* that there are more calories coming in than there really are, so when the calories don't show up, the body is like WTF FEED ME and you usually wind up overeating later.
The sugar (i.e. high fructose corn syrup) in drinks today is outrageous. I stick with water or milk, and that is it. Sometimes I will drink an unsweetened, caffeine free tea or coffee, but that is really it. Boring and dull? Yes... Better on my waistline? Definitely!
'11 BMW E92 ///M3 - ZCP and DCT
'13 Toyota Tundra - 4x4 Platinum CrewMax, 5.7l iForce V8