Hello Alison, I'm Dr. Deb and will do my best to help you today.
I'm sorry that Coco is having this problem; I know how distressing it can be.
This behavior is called coprophagia....the ingestion of one's own stool or the stool of another animal.
It's certainly a disgusting habit but it's actually a fairly common one, believe it or not.
We often don't have a good understanding of why some dogs engage in this behavior although it's rarely related to deficiencies in the diet.Many puppies go through an oral stage in which they explore everything with their mouths, sometimes ingesting a variety of non-food items, including feces.
As they mature, though, the majority of pups eventually learn that food tastes better than feces and that's the end of it.
But for those dogs who continue the practice, there may be a compulsive component as to why they don't stop. It's almost an addiction, in a way. And, as a result, it's often very difficult to break this habit as it is for most compulsions.
The products which you're tried which are available as Forbid or S.E.P. (stop eating poop) here in the States may help some dogs but in my experience, they don't help the majority of them. Some owners swear by fresh pineapple. But your experience with these things is what I routinely hear from clients who've tried them: they don't work!
Some people will try to sabotage the feces by adding jalapeno peppers or something really spicy to the stool. Others will add Accent or meat tenderizer to the kibble.
Brewers's yeast and apple cider vinegar are not likely to be effective either, unfortunately, but won't be harmful if you wanted to try them; I'm skeptical that they will actually make a difference, though, since the other products you tried were ineffective.
Personally (and I do mean personally since I've had several dogs through the years who've done this and am currently living with one who does) the only thing that I've found that consistently works is to pick up the stool as soon as it's produced. If it's not there for a dog to ingest, then they don't ingest it.
You can also teach the "leave it" command which works if they start to eat the feces in front of you. This is a good command to learn anyway, in my opinion.
Of course, these methods will only work if you are present. For those times that you are not, I have resorted to a basket muzzle and often suggest them to owners if they are open to the idea.
I also encourage lots of exercise and quality time with their owners; boredom is not necessarily associated with this problem but it helps to rule it out by keeping the dogs active.
This can be an extremely difficult habit to break (as most OCD-type behaviors are) ....and a frustrating one to deal with as well.
This is basically the equivalent of food poisoning so I try to discourage it as much as possible....not to mention how disgusting it is.
I would dearly love to be able to provide a solution to this problem which will be 100% effective but, unfortunately, we don't have a solution which works for every dog. Believe me, I've tried everything suggested, recommended or guaranteed to work for this problem and have yet to find anything which consistently works. Deb