My star tortoise won't drink. What food is best for healthy growth?

A star tortoise will readily drink standing water. Provide a shallow bowl of fresh water. Clean and refill the bowl daily. Confirm proper temps in the enclosure. Star tortoises do best in temps between 80 F and 90 F with a basking area of 95 F. Temperature plays an important role in appetite and activity. If he doesn't drink, you can soak him once or twice weekly in warm water or a 50/50 solution of water and unflavored PediaLyte. Soaks can last between 15-30 minutes.
Star tortoises require a high fiber diet that is rich in calcium. Feed a varied diet including grasses, vegetables and greens for optimal growth. Grasses that can be fed include, fescue, blue grass, mature alfalfa or Bermuda grass. Vegetables offered can be pumpkin, squash, peas, mushroom or bell peppers. Greens include collard/turnip/mustard greens, dandelions, escarole and grape leaves.
The above foods make up a partial list of acceptable items. It is by no means all inclusive. If your tortoise does not begin drinking on his own, consider an exam with an experienced herp veterinarian.