What does Doctor Cox mean You don't drink Scotch?

Answer 1

JD was trying to be cool and drink a little but Dr Cox knew how much he hated beer and so it's obvious he doesn't drink Scotch. So just as JD took a sip, Dr Cox reminded him that he doesn't drink Scotch, as in, he doesn't like it. So JD spit it out.

[edit]

While the above is entirely possible, the way Dr. Cox says it and the context implies otherwise. Dr. Cox wouldn't really know nor care about JD's drinking habits- he is known to imbibe an appletini (easy on the tini), so another hard liquor like scotch, though unlikely, isn't out of the question.

Cox emphasizes the word "drink" and is a seasoned scotch drinker, so he probably means that scotch is a drink to be gently sipped, not gulped in the quantity that JD took (clearly not knowing that scotch is a rough liquor and not a delicious butterscotch-like liqueur). "You don't DRINK scotch", you sip it.

[re-edit]

No, the first answer was correct. Dr. Cox would certainly be aware that Scotch would be entirely inconsistent with "Girl Name's" drinking habits. The second answer's suggestion that Scotch is along the same lines of an appletini is wrong and offensive on so many levels. He clearly emphasized the "you" as applying to JD, which set up the joke of JD spitting it out in disgust.