vitamin water?
 I don't see why not, the calories are ok if you're getting some nutrition from it, at least I think so anyways.  I have orange crystal light that has like vitamin c in it, I figure that's really better than the other kinds that have nothing in them.  have you tried the special k water yet?  I haven't, but I've heard it's supposed to have protein in it. 
 I have drank a whole one without any trouble at all. During the first week my doc recommended some gatorade which has more sugar than this vitamin water so I figured hey what the heck i'll try it. Well low and behold I have not had a problem with either of them. ~ well I havnt had a problem really with anything. I drank some orange juice and that was fine also. 
                                                   Jenn