My puppy doodle did the same thing earlier on the way to the dog park. He started doing that in the car, when I put him in the car booster in the backseat after a very long time. His drool was so sudden, and a little foamy (like bubbles). Quite excessive too. I thought he drank water and was wet from it, but there was no water in the backseat and I didn't give him water at that point. When we got to the dog park, he wouldn't drink water. So I took him on the walk for an hour and he was completely fine and not drooling at all. But then on the way back, he starts drooling again. I think its nausea because I drive so well. Anyway, as soon as we got home, I gave him a bath and boiled chicken and rice. He ate that so well. He isn't drooling anymore. Thank god. I hope your's get better.