I have a pit-bull his name is Harley, is it bad to give dogs hot dogs?

I also feed him science diet...HE HATES IT!!!! I feel so bad because I love him so and I want the best for him, what is the best food for my pit? he is 2years and one month., he seems sluggish at times, and other times he is active, I always think that he looks sad, please help me to help him, he is all I have, and again I love him so, he is a major part in my life, and I would do anything I could for him. thank you.