I have, but let me also say that I buy treats and food for my dog which are fit for human consumption in the first place.
The few "dog chocolate" treats that I have seen are made from carob, an edible legume in the pea family. It's commonly used in vegan food as a substitute for chocolate (which contains milk...a vegan no-no) because of its sweetness.
I wouldn't say that the treats for dogs tasted like chocolate though a few smelled similar to chocolate. Of course, most dog treats smell great but taste like cardboard--not surprising as dogs have a far superior sense of smell to us but lack taste buds.
Victoria Lynn, your answer would make a good question in it's own right!