If he is very lethargic, a vet visit may be in order in case his blood sugar is low and is not rebounding. Also, dehydration must be a concern. If a vet visit is not possible. You can treat the diarrhea with a teaspoon of kaopectate 2-3 times daily. The clear foXXXXX XXXXXquid may be some bile that was vomited up. You can try to give a 1/4 tablet of pepcid AC, or tagament twice daily. This may help with the vomiting by reducing acid production in the stomach. You can also support hydration and nutrition with some pedialyte. However, any decline his condition is a reason for a immediate vet visit. I hope this helps and gives you direction.
Parvo is definitely a possibility especially if he has never been vaccinated. Certainly, parasites are also possible. If he lethargic, I would not treat this casually and watch him close. It may be worth a ER vet visit.
I hope this helps
by the way great name for a yorkie!!