Pill form of MDMA, also known as ecstasy. Beans are usually sold at $10 or less a pop, and generally much cheaper than pure MDMA because beans are cut or produced with a small percentage of cocaine or heroin to dilute the content. Because beans are produced illegally and on the black market, it's almost impossible to determine the actual percentage of MDMA used in any given pill.
"Let's roll on some beans at the rave tonight."
"Man I just took a bean, I'm rollin' hard."
"I popped three beans on Thursday and haven't slept since."