Hello XXXXXXXXXX,
This is Dr. Christian.
There are some natural things you can try for diarrhea. Canned pumpkin (the fiber helps) and plain yogurt (no artifical sweeteners) with active cultures of lactobacillus (activia is an example) can be given. You can try some immodium but it is only a temporary fix. Try tempting her to eat with chicken breast, white rice and scrambled eggs in small, frequent amounts. They are easy on the stomach. You can offer warm chicken broth to get more fluids in her. Since she is not eating and has vomited I would recommend she be seen by a vet. Schnauzers are somewhat prone to getting pancreatitis which has the potential to worsen dramatically if not treated in a timely fashion. She could just have an upset stomach but there is no way to know if it is pancreatitis without bloodwork. Here's a link about pancreatitis: http://www.petplace.com/dogs/acute-pancreatitis-in-dogs/page1.aspx
If you let me know her weight I'll give you a dose of immodium you can try.
You can give 1 1/2 teaspoons of Immodium AD every 8 hours but make sure the label is correct. It should read:
Dog Veterinarian
12 years of veterinary experience in canine surgery, medicine and behavior