Yes, you can and should brush his teeth every day.
Now, with that said, as Taylor mentioned, have your vet check his mouth because if it stinks really bad, it could have an infection and/or need a dental. These Yorkies are prone to bad teeth issues, sadly.
To brush his teeth, you can use C.E.T. toothpaste (one of several choices). I use this and follow up with a brushing with Coconut Oil due to its antibacterial and antifungal properties. Smells yummy, too
