Do you think he refuses food because he doesn't feel well, or has nausea, or stomach problems? Or is just basically, being fussy? If you think he might not feel well, then take him to see the vet. If it's fussiness....Is he really good and hungry when he gets fed?
(When I was a kid, I used to ask for ketchup sauce with my food. My mother(who couldn't afford anything but basics) used to say "Hunger is the best of all sauces") She was right. When I was good and hungry even dry bread tasted wonderful!
My aunt has a cat that is a picky eater. The more foods she tries to entice it with, the worse it gets. That cat is not hungry. I can tell by looking at it. It is overweight. It has no health problems...yet...One day she will try chicken. Then the cat won't eat chicken, so she tries steamed fish, and the cat picks at it, so she tries premium pouch cat food, roast pork, salmon,......same old story. In the meantime my aunt tries every food under the sun to try and entice a cat that has no real appetite.The cat doesn't have regular mealtimes, with hours in between, it is given food willy-nilly, all through the day, and into the night. I am not saying you feed your dog like this. I'm sure you don't. But once you begin to pander to 'eating moods', it's a slippery slope!
It might be an idea to choose a food that is good for your dog, -(Science diet if you believe that is the best for him)- and will not irritate his stomach, and that you are happy with nutritionally, then just give him the food at mealtime. If he doesn't eat, leave the food down for 10 minutes, then take it away. Give nothing at all until the next mealtime, then give the same food. If the same thing happens, repeat the procedure without wavering. He will soon get very hungry, and I am sure will eat it, and enjoy it.
Dogs have a different attitude to their food than humans. Sometimes we fancy Pizza, sometimes Chinese....etc. Dogs aren't like that. If they are hungry they will eat usually. Whatever you give them.
My dog loves Reduced Fat Evo, (dry) and also loves Nature's Variety (raw frozen)- rabbit is her favorite. Also loves raw frozen bison burgers from Walmart. (it doesn't take that long to thaw raw frozen- or just leave in fridge overnight- ready to go in the morning).
Rabbit is so good for dogs. As it is a game meat, it has no fat. Under the skin of a rabbit you'll find not even a speck of fat! Watch for the bones though. They are very fine and splintery, a bit like chicken bones. Not a good idea!