The Chi Chi diet will need to include animal proteins, healthy carbs, vitamins and minerals, and omega fatty acids--nutrients every dog needs to maintain its health in the long term. This means the best Chi Chi dog food is premium dry kibble, as it contains balanced portions of the above-listed ingredients.
These hybrids do best with food formulated for toy breeds. Royal Canin and Nutro are recommended brands that carry excellent lines of premium toy-breed food.
Adult Chi Chis will only need about a cup of dry food per day, divided into two meals. Chi Chi puppies will need a bit less: depending on age, about ¾ cup per day, divided into three meals (not two) until five months of age.
For more info on feeding a Chi Chi, see this chart:
Dog AgeDog WeightFood TypeAmountFrequency6 Weeks>1 lbDry (Puppy formula)4-6 pieces3x/day10 Weeks1.5 lbsDry6-8 pieces3x/day5 Months3 lbsDry0.25 cups3x/day8 Months6 lbsDry* (Puppy/Adult)0.4 cups2x/day10 Months+8 lbsDry (Adult formula)0.5 cups2x/day*--Around this time, transition to adult food by mixing in adult formula with the puppy formula, in slowly increasing amounts with each meal, for one week.
Try if possible to stick to the above-listed portions. If these hybrids are constantly overfed (and under-exercised) they can become overweight--and a fat Chi Chi will have numerous health problems and a potentially shortened lifespan. You can help control your Chi Chi's weight by having consistent feeding and exercise schedules, by not feeding the dog table scraps, and by not leaving food in the dog's bowl all the time.
If you're worried your Chi Chi is overweight, try this test: run a hand along the dog's side, and if you can't easily feel ribs, it's diet time--which means less food and more exercise!