“And if it runs out I can stop at a drug-store. You can buy anything at a drug-store nowadays.”
This is one of Tom’s greatest digs at Gatsby. Tom had recently found out that Gatsby was the owner of many drug stores, and sold bootleg alcohol at these stores. So he’s making a not so subtle reference to that fact and it ends up being pretty effective in silencing Gatsby.
To help improve the meaning of these lyrics, visit “The Great Gatsby (Chapter VII)” by F. Scott Fitzgerald and leave a comment on the lyrics box