Its not documented, but a month or two back, the food/drink serving NPCs (Rychek, Metal-Mouth Sally, etc) were made smart enough to remember the last drink you purchased from them. That let them respond to requests 'for another' and so on.
We'll, tonight, thanks to Kevlar's thinking and my coding, they now will remember what you last asked for. This means that you can order a 'sandwich' and Sally can tell you that she 'can get you a cajun, an original or a BBQ' and you can then tell her 'cajun' and she'll know to get you a cajun sandwich.
Kev noticed that you guys already order like this and then are forced to learn it the hard way, so it was a good idea to support the manner in which you were already ordering.
Additionally, bartenders can tell you what is on the menu and how well business is doing. Just ask.