The Basics
Nutrition and hydration around cycling is important so that you feel comfortable and are well fuelled when you are out riding.
it’s a good idea to eat a well balanced meal around two hours in advance so that you can properly digest the food and utilise its energy. You should also take on fluids pre and post ride to replace water lost as sweat.

Hydrate and fuel before you train and compete, your body will respond better to exercise, and your muscles will have more energy. That means you can train/race longer and harder without running out of fuel and help prevent cramp along with faster recovery and less chance of injury.

Drink to replace fluid loss through Sweating
Drinking fluids during exercise at a rate that prevents you from losing more than 2% of your body weight,
this will avert dehydration, which will impair your performance.

Sports Drinks have many advantages over water when training at high intensity lasting an hour or more.

• A sports drink provides carbohydrates to help sustain blood glucose level during exercise.
• A flavored sports drink leads to greater fluid consumption during exercise.
• Sodium and carbohydrates help the fluid in the drink to be absorbed more quickly.
• Potassium replacement off sets leg cramps, Leg cramps can stem from a potassium deficiency.

Whether to take in carbohydrates or not during exercise depends on the length and intensity of exercise:

For exercise sessions of up to 60 minutes, and of low intensity you generally have adequate carbohydrate reserves on board, so you don't need to consume carbs during exercise.

For moderate to high-intensity exercise of 60 minutes or more, 50 grams of carbs per hour is recommended, with small amounts consumed frequently.

ie made up in a sports drink consumed every 10 minutes after the first 20 to 30 minutes of exercise.

We Recommend
on a ride of 50 miles about 2.5 hours to 3 hours of riding you would want to drink 2 x 500 ml carbohydrate drink and carry a carbohydrate power bar in reserve, should you get the Bonk.

The Bonk, when your glucose levels are depleted and you get wobbly legs.
Here is a well written and extensive guide about food, nutrition, vitamins & diet