My dog did too! I put a tiny bit of mouthwash in his water( just a tiny bit!) and that did the trick. Mouthwash is fine to ingest in such small amounts and you don’t have to pay for the stuff at the pet store, of course if you want to you can. I also brushed his teeth. I only had to do it once. I just used my regular toothpaste. If his breath remains bad after this you might want to ask a vet to be sure it’s not an infected tooth or some other dental issue. Hope this helps!