There is some evidence that caffeine (contained in significant quantities in coffee) is a diuretic - i.e. it causes an actual increase in the volume of urine discharged.
However, different sources of evidence have proved somewhat contradictory so it is perhaps best to say it is inconclusive - particularly in relation to the "dosage" levels required to create the diuretic effect, and whether the effect is preserved if the coffee (or other caffeine source) is ingested regularly on a daily basis.
As caffeine is also a known "stimulant", it is also possible that it creates a sense of "urgency" to urinate when the bladder is not sufficiently full to create that sense of urgency in the absence of caffeine.
Personally I do not experience any increase in the volume of urine, or (as far as I am aware) any feeling of increased need to urinate as a result of drinking coffee. However, I am an infrequent drinker of coffee - rarely drinking coffee on more than one day per week, but when I do drink it, it is typically a large mug full ( around 400mℓ ) made more strongly than average.
Caffeine and tea are diuretics. They make you wanna pee more because it somehow prevents water reabsorption.
So when you go for a workout, don't drink Iced tea and caffeine-containing stuffs. You're gonna sweat even more.
Oddly I get the same feeling when I drink large amounts of ordinary water.
It is widely considered to be but the medical evidence is inconclusive.
Interesting, I never new that, thx :-)
Coffee is a natural diuretic.