It sounds like reverse sneezing to me. I've had several different toys breeds (and many yorkies) stay here as fosters and each of them sounds a little different with their reverse sneezing. I have found very gently rubbing their throat for a second usually stops it......Or, I will step outside with them, something about the change of environment seems to make them stop.
Also, with an empty tummy it's not too unusual for a yorkie to vomit the yellow foamy bile in the mornings. You might try making certain they eat first thing in the morning and a little snack at night before bed has helped here.
Hope this helps or you can get some answers for your peace of mind.
__________________  ~Ruby, Reno, Razz, & Jack~ |