Grapes cut in quarters without seeds provide needed moisture. The best way to prepare his food is with a food processor. The reason a food processor works best is because iguanas are smart creatures. They will pick out their favorite foods and leave the other stuff in the dish. He is not getting the balance he needs if he is only eating his favorite foods.
Iguanas require a small amount of protein in their diets.
You can provide this in one of two ways. Either crumble boiled egg whites onto his food once a week, or purchase crickets and let him catch them. The most important aspect of an iguana's diet is balance. Be absolutely sure to give him vitamins and a variety of healthy foods. These are all signs of Metabolic Bone Disease.