Very Picky Eater

I need help with my little brussels griffon!He is the pickiest eater!...he is also proned to hypoglycemia…i can’t find a food he likes!...anyone have suggestions?...i give him a paste called NutriCal to help keep his blood sugar levels up…the only thing he kind likes is when i heat up a little bit of Purina Pro Chicken and rice for puppies…we’ve already been to the hospital once since i have had him…I just want my pup to be healthy!