I reckon it's never too early to start teaching them things like sit & a few of the basics, although I've never had a pup as young as 5 weeks so I can't be sure exactly I started teaching Monty sit etc when we got him at about 8 weeks old. What I did for treats was, I got one of the small puppy stick thingys, think they were pedigree, and cut it into small bite-sized pieces for him as a pup. Found it worked perfectly. Maybe if he really likes the bread, you could use that as a treat? Sorry I can't be of more help!