[Sunnydayz]

I took Gizmo to the vet for the same type of cough/sneeze, and the vet explained things very well to me. He told me that the shots they get, purposely make them get a cold every week, as that is how they become immune to them.

Also the smaller the puppy, the smaller the lungs. If your pup was not used to long energetic play before you received him, his lungs could be weak and need to be built up.
Gizmo was super hyper, so every time he would do it, I would put him in his xpen to nap. Well the vet told me I was ruining hs fun and stopping the strengthening of his lungs, and the dr me to stop taking his play away. Sure enough, it took about a week and he no longer did it, as apparently it did strengthen his lungs :-) he has not done it since after about a week of this, and I haven't had any issues with it since. This could be the case with your pup :-)