What do you do when your dog has no appetite？

I don't believe giving the dog cold water before eating will cause diarrhea unless the water isn't clean and contaminated from whatever dirty source. Remember to clean the water bowl often.

As for getting a dog with no appetite, you could add a little wet dog food to the dry dog food and mix it up. Or add some cooked chicken meat. Or add some olive oil to the dry dog food. Any of these techniques are used to get the dog's saliva glands rolling along and kind of subliminally get the dog to realize he or she is actually hungry. The fat in the wet dog food, the chicken, or the oil is supposed to hit the dog's sense of smell before he starts to eat and that gets the dog to start salivating.

It's normal for dogs to eat less in hot days. Mine just eats a lot of frozen dog treats. He drinks a lot of water and doesn't eat much, but he is energetic as ever.

A dog isn't going to starve himself, but perhaps you should take him to the Vet.

Dogs as they get older do sometimes have eating problems as do people where they don't take in the appropriate amount of calories per day. That said the original poster needs to give the dogs breed and age to help us figure if he should worry about the dog's summer time appetite.

Vitamin B is an appetite stimulant for stock nimals and pets.
When it gets real hot, they will tell you theyre not hungry but if it goes on for more than a few days, there may be something wrong an the vet trip is always a good idea.

If this continues for any longer, see the vet. It could be a number of things, and the worst case scenario, an onset of some illness.

We have three dogs and feed them in the morning, two of them you can’t put the food in the bowl fast enough. The third one is very picky, would never eat. She didn’t like eating in the morning, you put her bowl out in the evening and she gobbles it up.

But I agree, if it continues you might need to take him to the Vet.

How much exercise is the dog getting? A dog should work for his/her food.
If the hound is getting out for regular walks or runs and is still not eating, take it to the vet.

Take him to the vet and find out what's wrong.

Thank you for these good suggestions, maybe I am too busy to take my dog out for enough exercises, so it have not many consumption of calories, so he does not hungry.

Yes a dog will starve himself. Mine is.