Avoid eating during the final 2 hours before the race, if you need to - drink a carbo type drink. If your is race is in the afternoon, eat a meal 2 - 3 hours before it. Avoid sweets or sugar type foods before you race. What to Drink - Always drink plenty of fluids when training. It is important to start a race well hydrated, drink fluids up to an hour before the start.
Water is good for short races and essential in hot summer days.
For longer races, use a Carbo drink like Maxim, etc. It is important to replace fluids as quickly as possible after racing to aid recovery. The pre-ride will help you decide on your choice of gearing, your line in the single track sections and turns etc. On the day before the event give it a good going over, check the wheels and everything is working fine, avoid fitting a new chain or sprockets, shoes or cleats without trying them on a training ride. Also stretch before the start.