This Sunday is too late for you to change anything from what you have done (and know worked) in training. Knowledge in this area will make or break your race day efforts.
The next time around the following may help:
Fueling is broken down into 8 major areas:
1. Trying different things in training - with focus on your long brick workouts.
Knowing what works here is the "dress rehearsal" for race day.
2. Your taper:
This is where you get your proper sleep, fluids and carbs.
3. Pre-race meal:
This is the night prior in marathons and 1/2 Ironman events or in the case of an Ironman distance 2-days prior. This is the "Carbo - Loading meal" Knowing what works best for you is a matter of personal experience. I supplement Gatorade Energy Drink. Not your standard Gatorade either...this stuff is only available over the web and by the case. It used to be called Torque but the formulation is pretty much the same about 80g of carbs in a small drink. I use 3-4 of these, drinking one each day in the days leading up to the race, along with my meals.
4. Race morning meal:
Again this is lessons you should have learned in your long bricks. It should be something lite yet gives you a boost of energy for the race start. Mine is too unique to really be shared here and something I have worked on for many years.
5. Race day fueling during the event:
Again this is a lesson you should have learned in your training and long bricks. The key here is to know your sweat rate or how much your body weight drops over a given time of race level exertion within given weather conditions. Breaking down the event to the following:
Bike pre loading and fuel intake on the bike (I always say feast on the bike! Enter T2 fueled and ready to attack the run).
For an Ironman event you have your special needs bags to consider as well.
a - d
are things you can contol where you can plan what you will take and when. I use various E-Caps, Hammer products and special things that I know help me.
Another factor is to have trained with and understand what products will be offered in the given event. When I first did Ironman Hawaii in the late 1980's they offered Exceed as the energy drink so I trained with that product. For the Boston Marathon they use Gatorade, for MCM (Marine Corps Marathon) and Walt Disney Marathon use Powerade. Understanding how you perform and tolerate the various products offered on race day is an area where many fail to do their homework.
6. Immediate post race recovery:
Know works for you, for me it is a Hammer Product, re-hydration and other products from E-caps.
7. The week following the race:
This is a very important time for rebuilding of what you just tore down. Rest and Recovery is key, how much depends on the length and effort of your event. I have run several events very close together some back to back - knowing what to do and when to do it is critical
8. Have a plan B for the unplanned events that WILL happen - trust me.
Mother Nature related:
At one 1/2 IM I did in Boulder, Colorado the race day temps reached 98-degrees and not a cloud in the sky - Ouch! Many well prepared veteran Ironman athletes ended up walking over 1/2 of the 1/2-Marathon due to heat stroke/exhaustion, dehydration and for some just dropped out in T2 after a very difficult and hilly bike in the heat and at altitude.
At 1/2 IM Florida this year one of my "special" water bottles fell off the bike after going over a bump - lucky for me I consumed a full bottle as I ran my bike out of T1. So the one bottle still aboard got me to the first support stop.
There is alot more to Fueling but this is the basics - I cover much more with those I coach.
My experience comes from 3-IM events, 9-1/2 IM events, some 25+ Olympic events, 15 marathons (4 of which were Boston) and a ton of other races over 25 years of training and racing.
As far as "Race Strategy" - that's a whole different topic.
Good Luck on Sunday