Loki was super picky but it's getting better. Luckily we had no issues with low blood sugar so if he refused his food I just let him wait until the next day to eat - and he did. Since you can't do that, here are some random suggestions:
Add good quality low sodium chicken stock (not canned broth, get the good stuff in the box) to his food. It will make the food soft and irresistable.
Add Omega 3 fish oil - Loki loves this.
Does he like Cheese? We use cheese flavored Charlee Bear treats - he loves those. Most others make him sick.
Also, for treats try the Natural Balance meat rolls (PetCo) - they are like a big salami for dogs. Too salty to use for food, but OK for treats and better than things like puperoni.
Put Easy Cheese on his food. Gross right? But man they love the stuff. Same with peanut butter.
Try Innova Evo. I don't know what makes this food so good to them but man Loki can smell a sample bag of it a mile away. He is on a different food right now and I had considered switching him but I am happy with what he is on. He LOVES the taste of the evo. And, get sample packs. All of the good companies will give you samples. This way you don't waste food (although lots of places will take it back.) Try these companies:
http://www.canidae.com http://www.naturapet.com/display.php?d=inn-home http://www.naturalbalanceinc.com/ http://www.chickensoupforthepetloverssoul.com/
Try hand feeding OR try getting something called a Busy Buddy Twist & Treat:
http://www.busybuddytoys.com/moreinfo.cfm?Product_ID=2
Loki will refuse his dog food from his bowl but eat is from this silly toy. You just fill it with food and line up the hole and they kick it around and food comes out.
Also, try a different bowl or throw the food on the floor. Loki HATES the stainless steel bowl I got him and when I switched to a big ceramic bowl he will now eat out of his bowl. He also gets super excited about eating out of a paper bowl?? When I am washing his dishes I give him paper bowls and he loves them because he will eat all of his food and then steal the bowl and shred it! HA!!
Throwing the food on the floor works for lots of dogs, not sure why?
Finally, you can try taking the food away and trying to make him learn to eat when you feed him. Maybe offer it every 2 hours for 15 mins. If he doesn't eat - pick it up. I do this with Loki and if he is more interested in playing than eating I just let him see me go over and start to pick up his bowl and he will come and eat. I like him to eat on a regular schedule so this has helped me out. I don't let him graze.
Sorry for the randomness but I hope something helps!!!!!!