Water is the #1 thing you should always have on you! Unlike many other sports, swimmers don't see the sweat pouring off of them during a workout, but I promise you that you sweat! Hydrate yourself to maintain proper muscle function. Gatorade/powerade should be secondary to water at practice not an alternate for it!
Protein: Protein is essential for athletes to build lean muscle. Stick with fish and poultry. Nuts and Eggs are also a good source of protein for our vegetarians on the team.
Carbs: They get a bad rap, but Carbs are essential in the life of a swimmer, they are quick energy for meets. USA Swimming has an article that goes over why swimmers should be eating carbs and what types of carbs, read it here!
Meet Day Fuel:
Eat a healthy breakfast! It's the metabolism boost every swimmer needs! Try toast with peanut butter and a banana, oatmeal with low fat or skim milk, dry cereal, yogurt with fresh fruit. Do not eat something that your body is not used to! Eating at a hotel's continental breakfast is always hard, try to stick with toast, fresh fruit and dry cereal. Stay away from greasy foods like sausage and bacon or breakfast sandwiches from fast food restaurants, chances are they will not settle well on your stomach.
Cooler: ALWAYS pack a cooler for swim meets! Always pack plenty to keep your swimmer energized for the entire meet! Concessions at meets often do not have healthy foods for athletes. Bring plenty of water, some Gatorade or Powerade, fresh fruit and vegetables, cold pasta, power bars, cheese, peanut butter sandwiches, fruit juice, and crackers. Stay away from junk food - soda, candy, and desserts!
Recovery: Chocolate Milk (or regular milk) is an excellent source of vitamins, protein, and carbs! It will aid in muscle repair and will re-fuel them! If you are one of those swimmers with a high metabolism and are underweight, drink a protein shake after a practice or meet to add a little more protein that just milk.