When a guy cums in a girls ass and then urinates before pulling out. He adds a squirt or two of freshly squeezed lemon juice for added flavor and then allows it to harden for a day before removing it. The product is then broken up into small rocks and sold on the street for money and or sexual favors.
I needed some money, so I gave Jenny the Lemon Crack. We used the money to buy beer and porn.