We shall never know.
The coffee thing became a running joke - Cutty remarks in "The Savage Empire" that he could "sure use a cup of coffee." So the producers decided that his desire for coffee would be forever frustrated - note that in the briefing room scene in "The Tressaurian Intersection" he finds the coffee urn bone dry when he tries to pour a cup.
Also, Garrovick likes chili and coffee because that's what I had for dinner right before writing the other briefing room scene.
As I recall, what happened was I noted the "I could sure use a cup of coffee Quince" line in Savage Empire
and made a running gag in The Atlantis Invaders
of Cutty almost getting coffee, and even when he finally gets it, he doesn't get it. Dennis then added the empty carafe thing to TTI.