My mistake, you are absolutely right that it contains relatively little sodium -- however upon reviewing the facts upon your excellent suggestion, it is in fact a diuretic (due mainly to the caffeine content). Thus, it does very much cancel out the hydration it supposedly provides. So, yes I forgot the reason it works against itself but it very much does. So whereas drinking the equivalent amount of water would leave you satisfied an hour later, with Coke you may very well be going back to buy another bottle (also perhaps due to the crash from the initial sugar rush).

Coca Cola contains relatively little caffeine by fluid volume compared to, say, coffee. But more importantly, it's well documented that regular users of caffeine build up tolerance to its diuretic effects. From the Wikipedia page on caffeine:

"Most people who consume caffeine, however, ingest it daily. Regular users of caffeine have been shown to develop a strong tolerance to the diuretic effect,[34] and studies have generally failed to support the notion that ordinary consumption of caffeinated beverages contributes significantly to dehydration, even in athletes.[35][36][37]"

Here are the references:

[34] ^ a b c Maughan RJ, Griffin J (December 2003). "Caffeine ingestion and fluid balance: a review". J Hum Nutr Diet 16 (6): 411–20. doi:10.1046/j.1365-277X.2003.00477.x. PMID 19774754.

[35] ^ O'connor, Anahad (2008-03-04). "Really? The claim: caffeine causes dehydration". The New York Times. Retrieved 2009-08-03.

[36] ^ Armstrong LE, Casa DJ, Maresh CM, Ganio MS (July 2007). "Caffeine, fluid-electrolyte balance, temperature regulation, and exercise-heat tolerance". Exerc Sport Sci Rev 35 (3): 135–40. doi:10.1097/jes.0b013e3180a02cc1. PMID 17620932.

[37] ^ Armstrong LE, Pumerantz AC, Roti MW, Judelson DA, Watson G, Dias JC, Sokmen B, Casa DJ, Maresh CM, Lieberman H, Kellogg M (June 2005). "Fluid, electrolyte, and renal indices of hydration during 11 days of controlled caffeine consumption". Int J Sport Nutr Exerc Metab 15 (3): 252–65. PMID 16131696.

This is an incredibly thorough defense of a commercial soft-drink. You kind of sound like a coke dealer. Basically, all this stuff is bad because it gives you momentary pleasure at the cost of your long term health. It seems like splitting hairs to decide who to blame. Just say no.

Dude, I copy and pasted straight from Wikipedia. How exactly is that a thorough defense? I don't drink caffeinated beverages, so I haven't even got a dog in this hunt.

Any chance the added salt just makes it taste a little better? Maybe their scientists are working really hard at making coke taste really good (to the masses, IMHO all soda is gross)... which is addicting, because people like things that taste good?