Nice job man - going from 312 to doing an Olympic triathlon is a major accomplishment. For a sprint race you shouldn't need anything and are better off spending that time racing to get the best possible time...maybe a few swigs of gatorade on the ride but that's about it.
For the olympic, you should definitely be focused on carbs, minimal to no fat, avoiding fiber (you want nutrition that's accessible right now), and maybe minimal protein.
To be quite honest, though people tend to vilify these sorts of things in this forum, you should really consider products specifically for this purpose such as GU and Gatorate. The average Joe Blow has no business chugging Gatorade throughout the day at his office, but you will be in the special situation these products are designed for: quickly replenishing depleted glycogen stores and lost salt through presperation. Hi GI/GL fruit (yes, you read that right folks, high) is another good option, like blueberries or a banana. You wont even need that much. Good luck on your race.