>(Does it work on hubbies by any chance - a long journey with him wittering away)
My husband was sorely tempted to leave the pup, and me, on the hard shoulder!! Normally the most tolerant of men he was driven to distraction by a puppy that howled (really, really howled) for long stretches of time on our 4 hour journey home. I hadn't even thought of a DAP spray, worth a try!
Life got much quieter when I sat in the back seat with my arm in the crate. The puppy peed on my arm then fell asleep with his head up my sleeve!! He wasn't sick and not exactly distressed either just shouting - he's been a complete poppet in the car ever since with no sickness and blessedly quiet.
One of our other dogs, same breed, was very quiet on his 4 hour journey home but poo'd pee'd and was sick! He continued to suffer from travel sickness for several months after and he became a very noisy traveller too for a while.
Take plenty of towels, kitchen roll, newspaper, bin bags, water and a few toys for distraction if necessary. Try and use a crate with multiple doors for your convenience and set it up on the back seat (split seats are useful for this). Good luck with your new puppy :)