I wish Nikko liked Yorkie Yummies... great ingredients, and definitely the perfect size. He's not terribly fond of eating them though... If I give him one, he tosses it around like a toy for a few seconds, then ignores it! I got the beef liver variety though... maybe I'll try the other kind here soon.
Until then though, I discovered he LOVES chicken. His special potty treat is
Konas's Chips (dehydrated chicken chips) - email them and they'll send you a free sample (which is how I discovered Nikko liked them so well). The dehydrated chicken strips you normally get at a petstore are often made in China, and there are some pretty scary pieces of information surfacing about those so I'd definitely avoid them... but Konas's Chips are made in the US, from human grade chicken breasts. We've had plenty of other behavior issues arise with Nikko, but since these have become his special only-used-for-potties-outside treat, his indoor accidents have all but vanished. Totally awesome!
Another very special treat Nikko likes is what I call kibble cubes... I just half-way crush some of his kibble (so there's some powder, and some chunks still), put it in ice cube trays, fill the trays the rest of the way with water, then freeze. I figure these are the healthiest snack I can give him as a puppy - it's just his normal healthy and well-balanced food, plus water. And the cold of the ice seems to really feel good for his teething gums, which have a tendency to make him extra whiney and bite-y when they're bothering him.
Beyond that, he also loves cold raw baby carrots for munching on, and though I haven't tried this, many people like plain cheerios for treats.
Yorkies can be picky, I've learned, so try a variety of things if at first you don't succeed - just make sure you stick to safe foods (no onions, grapes, raisins, etc - there's a whole list of bad foods somewhere here on the forum).
Lauren & Nikko