I have this cookies for dogs. I would like to know if it's true that can clean teeth.
Honestly from reading the ingredients and thinking about dog treats in general I would say no.
Dog treats may slow down plaque build up as if it's quite a hard chew it will scrape the plaque off when the dog bites into the treat.
However, it would be the same idea of your dentist telling you to eat something really hard like bones and saying that it's sufficient to clean your teeth. So yes it may reduce plaque but it's not very reliable.
The most effective dental care for your dog is brushing his/her teeth.