Sparkling water or seltzer water that have no sodium won't cause water retention. I drink this stuff all the time! There are no artificial sweeteners in the water I drink, so not sure if that would be a factor.
There's lots of things in Diet Coke that aren't "food". Probably everything in Diet Coke. I quit drinking it but very occasionally. But to put it in perspective, a can of Diet Coke as 40 mg sodium, and a glass of milk has about 125 mg sodium.
Started 4/14/08 LINK TO PROGRESS PICS 1/1/2009
"It is impossible to live pleasurably without living wisely, well, and justly, and it is impossible to live wisely, well, and justly without living pleasurably" Epicurus