green tea is a diuretic... but it is hardly a stimulant. The caffein is actually canceled out by some other chemical, i forgot its name. other teas are diuretics but i dont know about the caffein cancelation.
Vitamin C is a diuretic for your backend ( it unconstipates you/makes you regular), so possibly vitamin C.
Creatine- it seems to make me piss more, even if i dont drink the extra water. I dont know what type of stimulant your talking about, so I put this here.