A. (by DrZakir): As far as vomiting is concerned our beloved Prophet Muhammad (peace be upon him) has said, “Anyone who vomits involuntary then he should not make up the fast but the person who vomits voluntary (i.e. vomits deliberately) then he has to make up for the fast.” So if someone vomits unintentionally the fast is not invalidated and he has to continue his fast but if someone vomits deliberately like putting a finger in his mouth and vomiting or pressing his stomach and vomiting or purposely smelling something which is very nasty and continues to do that and he vomits or he looks at something which is undesirable and keeps on looking at it till he vomits. So all these comes under the act of deliberate vomiting. Then you have to make up the fast.
Also if the vomit comes to your mouth and u again swallow it back into your stomach then it will break the fast. So if the vomit comes out involuntary, let the vomit come out, don’t suppress it otherwise it will break the fast even if the vomit was not intentional.