While Joe is correct in his statement I would like to respectfully disagree as that was the defining term for "dope wagon". Coming from a long line of relatives, including myself, having worked in the mills (Mayfair Mills circa 1973 to 1975), I was told by grandparents that the term "dope wagon" derived from the fact that the original formula for Coke contained a drug. The original contained coca leaves which in raw form were mildly euphoric I believe. Hence the word "dope" in the old southern term "soda dope". The cliche for taking a short break from work of going after a "dope and a pack of nab's" meant getting a soft drink and a pack of crackers, always on sale from the dope wagon.