Can Dogs Eat Veggie Hot Dogs?

It is not recommended for dogs to eat veggie hot dogs because of the ingredients used to make them.

Similar to regular hot dogs, vegetarian hot dogs should not be fed to your pooch. Instead of using animal intestines, the casing is made with cellulose or other plant-based materials. Meanwhile, the meat-free filling may consist of soy protein, wheat gluten, pea protein, or egg whites.

The soy found in veggie hot dogs can cause some pooches to become bloated or gassy, or to develop allergies or intolerances. Additionally, these meat alternatives usually contain toxic spices such as powdered onion and garlic. Canines that consume veggie hot dogs with harmful ingredients can show symptoms such as gastroenteritis and oxidative damage to the red blood cells. Vomiting, drooling, diarrhea, lethargy, pale gums, increased heart rate, increased respiratory rate, exercise intolerance, weakness, and collapse may also manifest within hours to a few days after intake. 

What to do if your dog accidentally eats a veggie hot dog: Determine how much was consumed by your dog. He may not exhibit any adverse effects depending on his size, how much he ate, and the ingredients found in it. Double check the nutrition facts label to guarantee it does not contain toxic seasonings. Get in touch with your veterinarian if your dog displays any of the signs listed above, or if there are any marked changes in his health and behaviour.

In summary: Because of the ingredients commonly used to make veggie hot dogs, the meat substitute is not advisable for dogs to eat. The condiments typically used to add flavour to veggie hot dogs—namely salt, pickles, onions, ketchup, and mustard—can also cause health problems when ingested by your canine. 

References:

Which Mock Meats and Other Vegan Foods Can Dogs Eat?

Can Dogs Eat Meat Substitutes?

Wikipedia: Vegetarian hot dog

Pet Poison Helpline: Onion

Dog poisoning: Signs of poisoning in dogs and what you need to do