Jeremy wasn't vomiting.He was just wretching after being given the whisky,and mixed with shock,it would make you heave. So the lie about him pretending to be sick,was just that,a lie.
Whisky can make anyone heave at the best of times if they're not used to drinking it.
Then after that,it was said he sat down to a hearty breakfast,which was another lie. Two curled up pieces of bacon and probably a bit of cheese off the trap ( sarcasm ) was all the food he had in because he ate at the farmhouse when he was there.