Sure, why not.
There is nothing beta about the act of buying someone a drink. It's a question of why you do it.
Jlaix's full "buy me a drink" response is "Oooh, I don't buy girls drinks. But I tell you what: if you make out with me, and you're good, then I'll buy you a drink."
And if they ARE good (read: they put feeling into it, and he can tell by the way they're kissing him that they're DTF), he might actually buy them the drink.
Really, when it comes to drinks, just make sure you aren't getting played. If a girl approaches you and asks you for a drink, like within a minute, she's trying to scam you. Getting the makeout first ensures that this isn't happening.
...of course, she might be scamming you even if she DOES make out with you, and may leave as soon as she gets the drink. But what the hell, you just got to make out with a hot chick for the cost of one drink. There are worse things to spend your money on.
