Sal's chipper mood faded somewhat at Sam's less than friendly reception. Not that Sal was about to hold it against him, because a) he was Sam, and b) he'd just been in Azkaban a couple of weeks before, and between those two factors, Sal could be infinitely, uncharacteristically forgiving.
"I have coke!" he said (somewhat artificially) brightly, holding up said substance for demonstration. Coke had to cheer Sam up. Who didn't get happy when they knew coke was coming?