He should add more of fruits and green vegetables to his diet. Because of diabetes he should avoid more sugary fruits like watermelon, pineapples. He should replace refined foods to whole grains food. Should add nuts, eggs to his diet, should add legumes and lentils to your diet, add tofu, low fatpaneer to his diet. Avoid alcohol, sugary drinks. Avoid fried food fully. Cut his sugar intake. These changes would help him surely.