The call button is for services, not just emergency. Idea is to minimize movement in flight. As long as you don't abuse it, I see no harm in using it to ask for a drink refill.

When BA FAs see how thirsty and well fed I am, they generally hand me two cans.

On UA you get the full can (my experience anyway).

Cheers. Sharon

I just ask. But I do it slyly...

"Ummm I'll have a can of coke zero, thanks".

Rather than, "I'll have coke zero...oh actually can I have the whole can?"

The only time I've ever not gotten it were if she/he didn't hear me, or if they were running out. Some airlines don't have cans also. From what I've seen Avianca is most bottles. They get Coke from a big 2 liter bottle and on the flight I was on last week coke zero from a 500ml bottle, which she then offered to me.

I always have politely asked for the entire can (including, specifically on UA, DL & WN) and I've never received any hesitation or negative reaction from the FA.

...and they would be wrong. A good FA knows that mind-reading is very difficult.

You're so worried about the possibility of being rude that you're making threads on the internet asking about it? Ask for what you want. You're a grown up. The FA's being grown ups too can answer yes or no. Don't be so worried about etiquette.

True.

Once airborne they can't even kick you off the plane easily. And on a late flight they won't risk a diversion to offload you simply because they might hate you for asking for a drink.

But I've only ever seen 150ml cans on BA, so two cans is still not as much sugar as one can on a US airline.

Fair enough.

But then which US airline does give you one whole can :p ?

When I fly American, I always ask for a can and I always get the can.

I'm actually surprised they would give you attitude for a measly can.

T tried it a few times on SQ. But the Singlish word for 'yes' is 'can', so the confusion that always ensued was rarely worth the amount of liquid extracted.

From very experienced intl. FAs who are familiar with other brands of English, I sometimes got an understanding "Can? Can can! .... can".

so try "im really thirsty could i have a large cola" and gesture with your hands a tall glass

I do wonder what that would get me ;) .... so I shall try.

I usually buy a bottled soda or seltzer (if I can find one) at one of the newsstands before my flight and bring that on board with me. That way i don't have to wait for the FA to come around, and I can put the cap back on and drink it throughout the entire flight.