@taly
This is what I do when I plan to travel any distance and in fact I did a 400 mile journey just three months ago and back repeating the plan each way.
I eat a hearty meal in the evening but not too late the day before travelling. Then the next morning I eat or drink nothing. Sometime i will have a small cup of coffee to get things started and then I make sure I basically empty my bowels. You know, go to the toilet and have a morning excretion like a lot of people do but I am patient so that I give myself time to basically have my lower intestines pretty empty. You get so you know when this occurs through experience. Then I eat or drink nothing and I do mean nothing. it would be nice to have a cup of coffee on the way but that is a No-no. I often go ten or eleven hours a day that way. my oncologist is 160 miles away and during that time I have while there bloodwork, an MRI , a Cat scan and see him and then I drive or am driven by a son back home. I eat or drink nothing all this time. Psychologically I think of it as my day to fast which is healthy and i know people used to do it for religious purposes so it isn't impossible or that hard. Mind over matter. Recently I tested it out on a journey to see my oncologist hoping things had changed perhaps. I had a Whopper. I thought things were good but a half hour later i had a fast inkling of trouble and before I could get to a restroom I had a slight "accident" and had to use what I call my "bag of tricks" to clean up in the clinic's restroom. No more experiments for me. I hope this helps you. I have had a few awful experiences this way but one has to expect it within an eleven year period. I am 80 years old now and so I have little desire now to travel except to see my oncologist.