Bike - carry multiple sources of water and an electrolyte drink (Gatorade is the most common but I like GU Brew) in separate bottles on your bike. I suggest getting a drink bottle for your aerobars such as this and putting your electrolyte drink in it. There are a couple different versions out there, I am sure the local shops have them. Water is to wash the sweet and sticky taste out of your mouth and off your hands but it should not be your primary source of fluids. Your electrolyte mix should be the source of your basic hydration. For calories you should start with a concoction I call "Ironman Cocktail" It consists of 3-4 scoops of Metabolol Endurance and 3-4 scoops of Cytomax mixed into a large waterbottle. (you can choose the flavors you might like) You can get these products on line (my friends at World Multisport put them together with Carbo Pro in a package deal), from GNC or your local shops might have them as well. Once the mix is made up it is quite "thick" so you don't drink it fast. Rather you take a sip every 10-15 minutes (set your watch to beep to remind you) so that you drink a full bottle through about 55-60 miles. At Ironman you will have a "Special Needs" pick up so you will be able to have another bottle waiting for you there. Supplement the Cocktail with one GU pack per hour (I like the heavily caffeinated stuff for racing), an Endurolyte every 30-45 minutes depending on how hot it is and how much you sweat. I don't like any solid foods such as Powerbars, Clif Bars etc. while training hard or racing. They are great for before or after but trying to digest solids while racing is too tough. If you are interested I have a sponsorship "deal" with Perfect Foods Bars, let me know and I can get you the discount code. The only exception I would make would be pieces of banana now and again or the chewy energy products coming on the market such as the GU Chomps (like a gummy bear but with "good stuff" inside) This strategy will work for training and racing.
Run training - carry your electrolyte drink and plan a route that allows you to pick up fluids as you go (especially once it starts getting hotter and the distances get further) Depending on the distance and the temperature I either wear my Fuel Belt or a belt that carries a full "bike sized" bottle like this. Carry a drink on every run, even the short easy ones and practice drinking every 8-12 minutes. Typically I drink a big bottle in an hour but have gone through two full bottles during the last 5 miles of a 20 miler in the heat. I find most people do not drink enough while training. During a race it is easier because you have aid stations every mile. As well, take a GU pack after 45 minutes and then another one every 30-45 minutes after that. Endurolyte tab every 30-45 minutes on the run as well.
Finally, one other note. On race day (and on a few long hot training rides and runs) good old Coke has saved my butt a number of times (they offer it at the aid stations of the longer events). The sugar and caffeine can be a great "pick me up" but the thing to know is once you start drinking Coke you really need to keep consuming it until the end of the event.
Nutrition (not transition) is the 4th event at a 70.3 & Ironman so you have to practice consuming calories during your training. You also need to practice taking in calories during your shorter training sessions when you are at or above race intensity. You might not "need" GU packs to complete a 90 minute training ride but something that works at lower intensity might not at race pace. Only by trying them at race intensity do you know if they will really work on race day.
