A lot has been written about nutrition for especially long distance runners. And every person/runner/athlete has an individual idea/plan for themselves.
I find it difficult to work out what would work for me.
I am preparing for a marathon, but I don’t often run further than 21 to 25 kms (I run 21/25 say 3 times per month). So when I run 33/35 I don’t know when and how much to eat/drink (before and during the training.) At approximately 25 kms I am totally “flat” – no energy, can almost not run anymore. I don’t like using Gels/Coke: it spikes my energy levels. Tried mostly bananas (which I think works for me), but not sure when and how much I should eat. Found Race Food too difficult to swallow during the race/training.
I understand your problem with long run nutrition and you are not alone, so many athletes have trouble with this.
Trouble with nutrition starts the day before so always make sure that you keep your nutrition regular, don’t change anything and don’t eat anything different, also eat well for dinner but please don’t over eat.
Next thing is breakfast, you have to eat at least 1.5 hours before your race, keep breakfast light but make sure it is energy rich. Peanut butter sandwiches are great but a bowl of oats or oat bars, bare in mind this all needs to be tried and tested.
Race nutrition is always the biggest challenge. First thing is make sure you have a strategy, set times or distances to eat and drink and stick to it. Now about your challenge, bananas are great but can be heavy on the tummy, try dates, they are high in energy and easy to eat, I have used 32gi chews and they are easy to chews, enerbee sachets are pure honey and are also an option, I use biltong and dry wors later in the race as I can’t handle the sweet anymore and they have sufficient salt in case you need it. If you set out a nutrition strategy then stick to it. As said above always try and test your nutrition on runs before you race.