Suggesions last: For training, you'll need to figure out Bubba's currency. It could be that you haven't found the right treat yet- have you tried cheese, liver treats, or hot dogs? Those are usually very high value. If Bubba is truly not food-motivated, try different toys.
And it's possible that in puppy K, anything won't be as alluring as other pups. We found giving Kimber a good play session right before class made her more focused in class. And as was said above, adjust your expectations for class. It should be for him to start learning how to behave in public- anything beyond that is gravy!