Hmm I don't know. When I was taking care of my aunt's dog, Oscar, in St. Louis. He started coughing up clear stuff and I just thought because he was drinking his water so fast. But when we came home one time there was puke all over the kitchen floor and it smelled bad, we saw some grass and cardboard in it. He didn't feel well at all and we phoned his vet. He said not to feed him anything that night so we didn't...in the morning we fed himi though and he was so excited lol, maybe there is something that Jake is trying to cough up but its not there yet...maybe he does need some grass just to get it out, if there is anything