Having a light dinner helps a lot. It takes around 24 hours for most of the food to be digested. Also, eat light meals on the afternoon and evening before the race.
As it takes time for food to digest and to get processed, try to avoid intake of food within 2 hours of a bike race. It is better to take a carbohydrate meal before the race, such as whole wheat grain bread, Oatmeal, pasta and pancakes. Do not have protein rich food as they will stay in your stomach for long. Do not allow food to stay back in your stomach when you are going for a bike race. Dairy food like cheese, milk, and yogurt should be avoided. Drink enough water as staying hydrated is important while bike racing.