Typically being sprayed by a skunk does not cause vomiting or diarrhea. A taste reaction from the skunk's spray could lead to nausea and drooling. Stress can sometimes cause gastrointestinal upset--was this a stressful event for your dog? Stress related or taste reactions should not cause signs that last for more than 1-2 days. Severe colitis (diarrhea) can lead to lethargy, vomiting, and anorexia.
Whatever the cause of the vomiting and diarrhea your dogs needs to be examined by a veterinarian and needs supportive care. Three days of not drinking or eating much leads to dehydration and negative energy balance. Your veterinarian can search for other causes of gastrointestinal upset, do a fecal and treat the diarrhea. If needed other medications to stimulate appetite or prevent vomiting can be prescribed.
Whatever the cause of the vomiting and diarrhea your dogs needs to be examined by a veterinarian and needs supportive care. Three days of not drinking or eating much leads to dehydration and negative energy balance. Your veterinarian can search for other causes of gastrointestinal upset, do a fecal and treat the diarrhea. If needed other medications to stimulate appetite or prevent vomiting can be prescribed.