Mimimomo, I only give Nena and Rufus treats as training rewards and as something for in between meals. I don't like giving Nena treats when she doesn't eat, I'm scared she'll just stop eating in order for me to give her treats.
We have sweet potatoes here, we normally by them for us and will start buying them for the doggies as well. We are familiar with the sweet potatoes, I just didn't understand what you meant with "I give them over-heaping teaspoon as a treat" but capt_noonie explained it