Just agreeing with everyone else here: cat should go to vet (or vet should come to cat, if you can arrange it), because of dehydration issues if nothing else. Tuna water is a great idea in the meanwhile.

OTOH, one of our cats pukes regularly, and it's just an expression of kitty dissatisfaction with the state of things -- usually with the flavor of food he's getting. So, cat pukes every few days for a week or so, Fishwhistle gets him a different kind of food, cat eats happily for a month or six weeks, and then the whole cycle begins anew. It's like a Disney movie, but smellier.