Blood capsules are used in an actor's mouth and he or she can bite it and spit out blood when the time is right. As for vomit... pick a soup flavor in the tan or green shades. Toss in chunks of ham or other meats or bread bits and you have realistic vomit. Ask the actor or actress what he or she is NOT allergic to or prefers and mix it up. Do some tests and see what works for you. Of course, for comedic projectile vomiting, you'll need a pump of some kind and some tubing hidden on the off-camera side of the actor's face and body. Good luck

What I tend to do is get about a mouthful of food (or less if you want less chunky) and then put a little bit of milk (or something else if you want a different color) and kind of spew it out in a vomit-like fashion. Maybe do multiple shots of it to make it look like they throw up for a longer period of time and it doesn't just look like they're spitting stuff out.