Well, pretend the bar serves something I'd drink. Say I'd get a virgin pina colada. I could imagine asking for one of those. I might also ask girls, if the environment gave me high enough priors on them being bi/gay.
So, your moral compass allows you to use other people's sexual preferences as a money pump?
(And no, that's not a line, although now that I've said it, I suppose it could be reworked into a LW-friendly response to a drink request. Needs more humor, less judgment, though! Hm, maybe "Are you trying to exploit my hardware preferences as a money pump?" A little too double-entrendreish, though. These things are really situational, and not at all suited to cached responses.)
I can't actually think of any situation where asking a question seems to me to be immoral. It can't be a denotative falsehood, so it's clear on the "lying" front; there's nothing else obvious it could be that would be wrong. I suppose it could be mean, or impolite, but this doesn't even appear to be that to me. I wouldn't badger anybody about buying me the beverage, which would be mean.
Followup to: Do you have High-Functioning Asperger's Syndrome?
LW reader Madbadger uses the metaphor of a GPU and a CPU in a desktop system to think about people with Asperger's Syndrome: general intelligence is like a CPU, being universal but only mediocre at any particular task, whereas the "social coprocessor" brainware in a Neurotypical brain is like a GPU: highly specialized but great at what it does. Neurotypical people are like computers with measly Pentium IV processors, but expensive Radeon HD 4890 GPUs. A High-functioning AS person is an Intel Core i7 Extreme Edition - with on-board graphics!
This analogy also covers the spectrum view of social/empathic abilities, you can think about having a weaker social coprocessor than average if you have some of the tendencies of AS but not others. You can even think of your score on the AQ Test as being like the Tom's Hardware Rating of your Coprocessor. (Lower numbers are better!).
If you lack that powerful social coprocessor, what can you do? Well, you'll have to run your social interactions "in software", i.e. explicitly reason through the complex human social game that most people play without ever really understanding. There are several tricks that a High-functioning AS person can use in this situation: