I read somewhere that Sai Baba told Kashiram to feed a black dog. Can you confirm this?

The source text does not support the claim that Sai Baba instructed Kashiram to feed a black dog. In fact, the texts describe a different act of charity recommended by another saint. Chapter 33 explains that Kashiram carried a bundle of powdered sugar because a saint named Janakidas Baba had advised him to feed sugar to ants. This bundle was so dear to him that he fought off robbers to protect it. Sai Baba's method for teaching Kashiram a spiritual lesson was unrelated to feeding animals; as detailed in Chapters 31 and 32, Maharaj addressed Kashiram's pride by demanding excessive Dakshina until he was humbled.