Last Friday I did my first ultra, a self-organized 50k. Things were going really well until about mile 25. By that point, I had eaten about 300 grams of carbs, which I knew was not enough, but I was doing good on hydration (still sweating and peeing). About 100 of those grams were from tailwind so I thought I was good on electrolytes too.
Then at mile 23 I met a friend who gave me a bunch of grapes, pita chips, a coke, and some peanut M&Ms. At this point I stopped counting carbs but I was probably still behind where I should have been. We ran together after that point, and I felt really good for the next two miles.
Then, I started feeling nauseous. At this point it was also getting hot (near 90F), and the trail was really exposed. I could run for about 5 minutes, then I'd feel nauseous, and have to walk for a bit. I drank a lot of water over the last 10 miles, about 1.5L. I stopped sweating a couple of times so I knew I was behind on hydration for that last stretch. My friend (an ultra veteran) kept giving me some chewable salt tabs. Other than those, tailwind, and a couple of cliff bloks, I didn't eat anything else for those last 8 to 10 miles.
My thinking is that I should have started on the electrolytes earlier when I knew it was going to get hot, drank a bunch more water when I stopped to meet my friend (other than the coke I didn't drink any fluids), and that hopefully that would have helped with nausea so I could have eaten more solid food over the last stretch of the run. Those last 10 miles were mostly downhill and I felt fine, so I know that if it hadn't been for the stomach issues I could have covered that ground a lot faster.
I know more experience is the only way to know for sure, but curious what others think, or other people's experience.