Yerba mate
From reports of personal experience with mate, its physiological effects are similar to (yet distinct from) coffee, tea, or guarana drinks. Users report a mental state of wakefulness, focus and alertness reminiscent of most stimulants. However, they often remark on mate's lack of the negative effects typically created by other such compounds, such as anxiety, diarrhea, "jitteriness", and heart palpitations. (The laxative effect of coffee derives from a substance that surrounds the raw bean, not the caffeine itself.)