RR just got to know why Eesha left him, and he is feeling sorry for her, feeling emotional on the situation, and maybe somewhere feeling guilty he misunderstood her, and she left him for his safety. So both are emotional, vulnerable, years of pains came out today in form of emotions. So I dont think it's anywhere wrong to drink with your ex, or a person you once loved with all your heart.
I think makers will go with the conspiracy theory instead of just 1 night stand, as the 1 night stand will make RR look like a sinner, and he will never be able to forgive himself.
So enjoy the track, this is just build up for the climax to come.