How is the running going?
There are some neat nutrition strategies you can implement during your training to try and get your stomach used to eating on the go. Some suggestions are;
1) If not already, simply eat during your runs, practice eating on the go, small amounts on a regular basis.
2) Eating a small meal or your breakfast and then going for a run (low intensity) within 15-30mins after eating. It may feel uncomfortable at the beginning but the trick is to do it more than once, even if you have to start out walking on your session.
Then as you get used to this you can eat before and then introduce eating regularly during (every 30mins from approx. 60mins into the session) on foods you feel you will be able to tolerate.
3) Practice eating during training and try if possible to simulate ‘race pace’, it is difficult to simulate that during a training session, but the nerves, adrenaline (and you will run quicker during a race) will influence appetite and the ability to eat.
4) I would question if you had any pre existing gut issues day to day and address those (and query any IBS, food intolerances, history of food poisoning, gastric bug etc).
5) Perhaps use low FODMAP food choices during a race (these are carbohydrate based foods that are low in specific sugars that can cause gut issues mainly seen in people who experience IBS, but may also be beneficial to those who have GI issues during a race).
6) Avoid NSAIDS during a race.
7) Are you over hydrated, over drinking during a race? And or eating too much simple carbohydrates e.g. sports drink, gels, gums (such as clif shot blocs), eating real food seems to be better tolerated for many e.g. pressed fruit and nut bars, watermelon (usually found at aid stations on ultra races), banana, trail mix, sweet bread style products, soups, pasta, pizza, rice pudding (but in small quantities).
Every one is so different on their food choices when it comes to ultra distance running, but hopefully people will give you some of their insights on here that may be helpful.
Hope your run training is going well!