Diuretic's force the body to shed extra water and possibly electrolytes. Thus a quick and slight weight loss could be noticed, but a cuppa probably woundnt be noticed on the average coffee consumer.
Ephridrine (in street form - "speed" or medicinally used as a cold and flu med, dieting agent and so on) in conjunction with some really strong coffee and or cola drinks, speed up the metabolism as well as create a nervous tension. It sets up the body for a fight or flight response. Thus the feeling of nausea, pent up energy and wakefulness. Pupil dilate, hearts starts racing and for some people a strong coffee alone will cause a feeling of missed heart beats (palpitations). Truck drivers, students, shift workers and the like are common users of ephridrine in some form in conjunction with coffee due to the effect.
With another diuretic on board, the water shed can be horrendous, and for body builders, this is perfect for definition. The aspirin (a non steriodal anti inflammatory with anti pyrexic and anti thrombolitic properties - reduces swelling without steroids, and minimises the bodys reaction to infection by controlling a normal rise in body temerature, and stops one of the bodys natural clotting mechanisms for up to seven days) for them though, is to stop the cells clotting as the dehydrated circulatory system tries to function.
The end result if they do pop something, they will potentially not be able to control the haemorrhage quickly enough, and the long term damage to kidneys with a hugely increased workload, is often a fast track to perminant dialysis.
Shame.... theres some nice bods out there too
They should stick with a nice coffee! Fresh ground beans perk'ed is best, it doesnt have all the other stuff to extend the quantity. Sounds like a good coffee question though (trundles off to do more research with coffee in hand).....