Not just any cough syrup, but PROMYTHAZINE cough syrup. Usually mixed with sprite, but has been known to be mixed with other sodas, mostly fruity ones such as fanta. Has a slightly grapey taste to it and is purple. Most people get addicted to this not just for the drowsiness affect that it gives, but because of its taste.
"Man, hold up... I got too much lean up in my cup."