Knowing that for most long distance events you “get what you’re given” at aid stations, I like to vary my nutrition a fair bit in training. This also has the advantage of allowing me to try out new things, knowing that the worse that will happen is getting dropped on a training ride. On the day, I start the way I always have with black coffee and brioche, washed down with a litre or so of Nuun as early as practical.
Overhydrating isn’t a major issue with a long swim in cold water to look forward to.
After trying out a few things, I have now settled on a fairly trusted regime of Clif shot Bloks and SaltStick salt tablets for the bike leg. This, I find, avoids the hunger associated with relying solely on gels for long rides, but still allows for racing light. They are also easy to constantly graze on throughout, ensuring there aren’t too many peaks and troughs.
Fluids wise, it's worth studying the course profile and aid station map in advance. Weymouth starts with its main climb shortly after transition, so I started with just enough fluid to get through to the aid station and re-bottled at that point.
For the marathon I generally carry five gels, in Weymouth this worked out as one for each lap (something to “look forward to” at the turn point) and a reserve for emergencies. This was topped up as needed from the aid stations.
I normally swear by a recovery shake at the finish, unfortunately lack of planning meant having to make do with the finish line beer, shame!
Varying the diet in training alongside mixing up sessions with “full” race nutrition and others depleted has really helped my stomach cope with long distance events. It has also meant having greater confidence that I can recover quickly in the event of any mid-race bonk.