Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Dave is feeling so poorly tonight, with loose stools, drooling and an episode of vomiting.
I can only imagine that he found something to eat that he should not have when he was outdoors earlier.
Drooling can be a sign of nausea, and the fact that he vomited supports that.
Because we don't know what he ingested it's hard to know how worried we should be.
You can give him acid reducers to try and settle his stomach in case this is related to nausea. Either:
1) Pepcid-ac (famotidine) at a dose of one 10mg tablet per 20 to 40 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one 20mg tablet per 40 to 80 pounds of body weight every 24 hours.
These will reduce stomach acid and should help settle his stomach. These are quite safe and can be used for several days if necessary.
A couple hours after one of the acid reducers is given you can offer small amounts of water or ice cubes to lick.
If that goes well then tomorrow start a bland diet of 1/3 boiled, lean hamburger (or boiled, white, skinless chicken) and 2/3 plain, boiled, white rice. Give small meals several times a day. If he seems to feel better feed the bland diet for several days, then start mixing in his regular diet and slowly convert him back over a period of 5 to 7 days.
If he attempting to vomit but unable to do so, his belly looks at all distended or he won't lay down and settle or he is pawing at his mouth or unable to drink water normally then I recommend he see a veterinarian immediately as this can also be a sign of bloat, a rare occurrence but life threatening if allowed to progress, or something stuck in his mouth.
If his drooling and vomiting continues in spite of using an acid reducer and a bland diet then he should see his veterinarian for an examination, some blood tests to look for underlying toxins leading to organ damage.
Please let me know if you have any further questions.