Guarana energy drinks and (for example Scitec) pure liquid Guarana are two different things, that's the reason I mentioned some brand. You need to try pure guarana. For me it's like 5-coffees at one 40ml shot, few hours lasting effect and no shaking. But be careful, you can overdose pretty quickly (start with recommended dosage on package and gradually add few milliliters each day to find your optimal/maximal dosage).