As I recall, things like coffee and ecstasy promote dehydration by making the uptake of water more inefficient. Also, I think your body has to filter out the nonwater parts of other drinks. I suspect that coffee is less efficient than water at hydrating you, but does not literally leave you with less water than you had before drinking it.
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As I recall, things like coffee and ecstasy promote dehydration by making the uptake of water more inefficient. Also, I think your body has to filter out the nonwater parts of other drinks. I suspect that coffee is less efficient than water at hydrating you, but does not literally leave you with less water than you had before drinking it.