Right context or never at all.
I use to be the guy that would buy chicks drinks like crazy. It never got me anywhere! I've literally had girls thank me for the drink then turn around and leave. I've had female friends tell me they have no money, go to a club and drink for free all night. I've had girlfriends go up to the bar to buy us some drinks come back cash in hand and a drink for me. Girls have drinks bought for them all the time! You've seen them huddled around the bars waiting for their chump to come along and save them from dry throat. Don't be the guy that is wasting his money.
This next part may be a little messed up, but it's the way I think. Maybe I'm weird. I get this strange satisfaction seeing the look on a girls face when I tell her that I don't buy drinks for women.
The look of complete shock and disappointment on their face is priceless and makes me feel so much better. If I was having an off night and was able to use this line, my super game powers would be restored and all would be well in the world of game for me. I've been in sets and needed to isolate. My exact words "I'm gonna go get a drink. Do you want to come with me?" To her I'm saying that I'm gonna buy her a drink, when I'm actually saying that I'm going to buy myself one and also asking if she'd like to tag alone. Now one would think that these girls would be completely turned off once they find out that I'm not buying them a drink. 90% of the time, they continue to stick around. Some will even offer to buy the next round.
Which brings me to my final point. The only time I will buy a girl a drink or a group of girls a drink is if they have bought a round for me or the group I'm with. This tends to happen when I've opened a set, established a connection and say "We should take some shots". When we get to the bar before the drinks are ordered I say "Alright... who's gonna take this one?" Watch for the deer in the headlights look. One of them will speak up and take it. At which point, you say that you will take the next one.
Anyway, just my two cents. DON'T BUY DRINKS FOR WOMEN! Unless they've bought you one.