Schutzhund tracking is often taught with food, foods which are semi-moist and can be broken into small pieces are ideal. The best foods have high attraction for the dog, are easy to handle and do not smell strongly. Ideally the food should not be easily seen. Small pieces (about the size of a quarter) of thawed frozen Bil Jac, dampened kibble, hot dogs chopped small or dehydrated meats work well. I have also found that some of the foods that come in chub format are easy to cut into small pieces for tracking. Happy Howies or Natural Balance chubs work very well, and are available from most pet stores.
When starting puppies, their usual kibble soaked for a few minutes typically works very well. You can stop soaking the kibble after the first few tracks, and for some dogs, kibble continues to work well throughout their lives. The advantage of kibble is that typically it has little scent and is dark in color so the dog learns to track the crushed vegetation scent and not by sight or scent of the tracking food.