you can feed crickets lettuce, other greens, carrots, apples, any kind of vegetable or fruit, except maybe onions and citrus. Fish food and grains like oatmeal can also be fed to them. High protein food like dog food or meat isn't good since crickets don't need that much protein. So I've heard.

I try not to use food that's too wet, like cooked food because it rots quickly and crickets die more easily then. I used to give my crickets moist cubes sold as cricket food but they seem to do better with grains and vegetables.