Limit eating out to 1 or 2 meals a day by staying in a hotel that offers a decent continental breakfast: cereal & milk, fruit, muffins, pastries, coffee & juice.
Don't be afraid to ask for a detailed menu, hours it is served (i.e. 7 am to 9 am) and if it is replenished. Alternatively, stay in a place that has a kitchenette so you can cook some easy meals: Cereal, Toast and Eggs, Chicken Caesar Salad or a Taco Bar. Pack good snacks to nibble when you are out sightseeing, i.e. trail mix, jerky, nuts, dry cereal, canned fruit cups or fresh fruit from local market. Lastly, pack a water bottle like a Platypus or Camelback, without the carrying pouch. Without the pouch, the bottles easily tuck into a smaller space, the water is a little warmer but still wet.