Here are some tips and advice for Marathon nutrition and Hydration.

A diet that generally consists of 70% carbohydrate, 20% protein, and 10% fat is about right for endurance events.
This is REALLY important for the two or three days heading into your long training runs and the marathon itself.

Make sure you drink about three to four litres of liquid per day. We recommend only drinking a sports drink (e.g. Endura) when training properly because it is not sugar-based and replaces all sodium and potassium you will sweat out during long runs.

Try this on the day of your long runs:

Eat two pieces of toast, a banana, and 500ml of sports drink three hours before you start
(even if it means getting up early and returning to bed). Then, don’t eat or drink anything
until you’re about to start at 7:30 am. This ensures you’ve finished your digestive process heading
out for your run. That process typically takes about two and a half hours.

Make sure you’re eating lots of good food and re-hydrating after long runs. Make sure you’re eating enough carbohydrates.

Make sure you drink about three to four litres of liquid per day. We recommend only drinking a sports drink when training properly because it is not sugar based and replaces all sodium and potassium
that you will sweat out during long runs.

We suggest the 70% / 20% / 10% rule mentioned in hint 1. One suggestion would be to eat a huge plate
of pancakes after a long run with lots of fruit and sports drinks. You need to do all of this within
about an hour of your long runs to ensure your maximising your recovery.

Perhaps consider wearing a Fuel Belt so that you’re hydrating on the run itself. Your body can absorb and use roughly a litre of liquid per hour during exercise and about 70 grams of carbohydrates.
We suggest applying that by taking gels at the start, at 10km, 20km, 30km, and 40km with 200ml of sports drink. Then we suggest taking 200ml of sports drink at 5km, 15km, 25km, and 35km.
Work out your own system but know this is one of, if not, the most critical element in not HITTING THE WALL!