The last time I had such a bad cough I couldn't sleep through the night, I just had two shots of whisky every time I woke up (approx. once an hour). It worked.
I didn't even feel hungover in the morning.
On a side note, I haven't had a drop of alcohol in about a month now. Month of university, nonetheless.
Unfortunately, my diet is still weird. It pretty much consists of Irn Bru, Ben&Jerry's and vegetable khichuri.