The dog's illness is not getting better

Give him some time to recover and wait around 12 hours before feeding him anything. Meanwhile, you can give him rice water in place of ordinary water. It might facilitate better digestion. Give him some vital minerals and energy-boosting carbs.

After a 12-hour fast, offer him simple, easily digested food, such as plain, boiled, skinless chicken, rice, and mashed potatoes. Serve it in a small amount and let it sit for a while. Increase it gradually if he don't vomit or exhibit any signs that the effects are getting worse.

If you don't see any positive changes in his condition, take him to the vet.

I also have a pet, this is useful information

It's probably best to take your dog to the veterinarian for a checkup.  

Try to make him fast for 12 to 24 hours but be sure that your dog is healthy enough to endure it. Since diarrhea can lead to dehydration so give him enough water. You can give him plain rice, boiled potato without skin, cottage cheese, pumpkin, etc. But never try to provide them with medication you don't know about always consult the vet before giving them any kind of medicine.