No matter the distance my pre-race breakfast consist of 1 white bagel with jam, a large banana, and two cups of coffee consumed 3-4 hours prior to my start time. The main purpose of this meal is to fill the pit in my stomach so I don't feel hungry and do it with easily digestible food so that digestion is done prior to the race. I also stop drinking fluids 2 hours prior to the race so I don't have to pee mid race, but that is another topic.
(I will use gels as an example but the source of nutrition is your choice)
30 minutes prior to the swim I will eat 1 caffeinated gel. At this point the pit is starting to return and I have been up for several hours so I eat the gel to appease the beast and wake up a little bit. On the bike I will have a bottle of plain water... that's it. I will stop drinking 20 minutes before the run to give the water a chance to absorb, I don't want anything in my stomach as I'm running. On the run I will dump water over my head to cool off and maybe sip some to wet my mouth but I won't drink any. There is no reason to take anything other than water during a sprint because even the slowest person should be done in under two hours, we'll get to that logic later.
Here I follow the same pre-race meal routine, and again consume the gel prior to the swim. On the bike I will have one bottle of plain water and I will consume 2-3 gels depending on how long the race should take me. under 2.5 hours 2 gels, over 3 gels. I will eat my first gel about 10 minutes into the bike, once I have settled in, and I will eat the second about an hour later 20 minutes prior to the run, again so that it is digested and my stomach is empty on the run. I want all my blood to be assisting my working muscles not being diverted to aid in digestion. Cramps occur when your body is fighting over who gets priority... your working muscles or your GI tract, the muscles usually win and your left with half digested nutrition and abdominal cramps. On the run most of the water is going over my head as I should be adequately hydrated from the bike for a 40 to 50 minute run.
Now, back to the reason why you don't need a buffet on your bike for short distances. Your body has enough glycogen to fuel about two hours of continuous exercise through oxidative glycosis (burning fat for fuel), about 2000 calories. If your event is under 2 hours there should be no need for extra calories, if your event is over 2 hours than you need to add extra fuel to the fire not replace the calories. Once the glycogen stored in your muscles and liver has run out you need to supplement with carbohydrates which act as "logs" in the fat burning process. Carbs should be consumed at a rate of about 30-60 grams (120-240 calories) per hour depending on sex and weight and unique physiological make up, I find a rate of 200 calories per hour works well for me.
Example: If I think I will finish an olympic distance race in 2 hours and 20 minutes I consume two gels over an hour bike ride totaling 200 calories, once I have run out of glycogen at the 2 hour mark I will have 50 grams of carbs to carry me though the run.
How many carbs you need to consume will also depend on how fast you will be able to finish the distance. An athlete finishing in 2:10 may only need one gel while a person finishing in 3:00 may need 3 or 4, it's all relative.
To sum it up, your nutrition goal should not be to replace all the calories you burn during a race but rather to add fuel to the fire when glycogen stores are running low. In the end, keep it simple.