not just cough syrup though...well, I have had it 2 ways...
The "real" way, or so I am led to believe: Codeine, Promythazine (spelling???), and sprite...I am 99% sure thats what is was, I don't think it had Robotusin in it, but it may have.
And the easy way: 1 part Nyquil, 1 part vodka, 2...