From Monkey Island wiki
Although StarBuccaneers does not serve grog, it serves grog-flavoured coffee drinks. Its featured coffee is the 'iced groggoccino': grog-flavoured coffee beans that are ground up over ice. It also offers free samples of a biscuits covered in StarBuccaneers Schmear Whiz (which Guybrush finds extremely revolting). There is also a mug (shaped very much like the silver monkey-head mug available at Planet Threepwood) visible in the window which can be taken from inside the building.
Guybrush can ask Otis if he wants 'a half-decaf, half-caf triple cappuccino mocha latte from Starbuccanners'. Otis doesn't want anything longer than his own name, so Guybrush asks if he wants grog, to which he replies in the affirmative.
Mabel, a tourist, despite confessing to having a StarBuccaneers store near home, spends all her time perusing the gifts in the coffee house. Her bag contains a cup that entitles her to free refills, which Guybrush can take.