If the race will last less than 90 minutes or so, you will, most likely, only need water or sports drink, perhaps a gel.  Longer than that will probably require you to take on some extra fuel.  How much you will need depends on you (it is a little different for everyone), but generally speaking, you will need at least 200 and as much as 600 calories per hour when cycling and a little less than that on the run.