Why Not Drink Coke?

So I'm really bad at remembering my water bottle, and whenever I forget my water bottle at home, I go to the cafeteria to buy a drink from the vending machine.  Each time this happens, it creates a nice mob of students who are all very interested in seeing what crazy foreigners drink.  Of course, the students point to the Coke and are like "トーマス先生！　coke!"  And expect me to get the only drink with Roman letters, but I never get the coke.  They are always super confused.  They ask; "Tomasu sensei, why not drink Coke?" and I reply, "In America, I can drink coke, in America, I can not drink Black Boss Coffee - decaffeinated and desegregated, for the equal opportunity executive suite."  They usually just give me a head tilt and look at me like "what the heck are you talking about?"

Although I feel like I do need to point out; I rarely get the coffee, I usually go for the tea or Pocari Sweat, but the label on the coffee is awesome..