Have you had him checked specifically for hyperthyroidism, blood glucose levels, blood pressure, kidneys, etc.? Has the vet run blood tests or just given a general overall "feel", checked heart rate, etc?
Our (formerly tubby) male cat was always sick at least a few times a week, and the vet said he was fine. He was eventually diagnosed with diabetes by a different vet, when we requested a full blood test. He was also diagnosed with kidney disease (common in diabetic cats) and hyperthyroidism (which can cause vomiting). Also, high blood pressure. Thankfully, now all being medicated and controlled - and the vomiting is rarely an issue (whereas before, it was nearly daily).
I'm not saying this to worry you, we just wish we'd caught it all earlier instead of thinking "oh he's just a cat that vomits".
Basically, with our cat, he would eat too much, too fast, because of underlying health issues causing him to feel hungry all the time. So we addressed it with slow feeders, timed feeders, etc., but didn't realise other things were happening.
Also not to be gross - but is the vomit basically full of food (indicates sensitivity or simply eating too fast)? Or is it more liquid-like and clear (indicates hunger)?
What kind of food do you feed him? Kibble, wet, or raw?
How old is he? And how much does he weigh? :)