It's not his reaction to the drinks that he needs to say sorry for. It's the fact that he took her there on his insistence, and left her alone while he partied with his friend. It's the fact that he for a second wondered where Kastur was, and then was easily willing it to let it go because of one sentence from someone who doesn't even know Kastur.
And it's the fact that afterwards, he barges off and goes and dances with his friend, leaving his wife alone, and then proceeds to make the biggest wrong of the night. This last part, I don't see him saying sorry for because as far as he knows Kastur doesn't know about it.
And Kastur said sorry to him. Maybe if he hadn't left her alone, in a place and situation she was uncomfortable in and felt out of place, she wouldn't have acted so rashly and quickly. To which she said sorry. But his reaction to that, and taking his third drink is fine.
But what he needs to remember afterwards is that she's the one who had to bear the brunt of his last such outing, while he took a shower.