I always find people who use this "I'll let x decide" shtick as complete utter morons.
Here's the thing: God already decided. He decided to give you laxatives so you can sort out your own bowel movements. God literally doesn't have time for your shit.
I need to survive for 3 days without pooping, and eating as little as possible. I can pee, but not very often. It can’t take up too much space. What food do I pack?
Please don’t ask why I need this.
It would be great if the food also made me sweat less.
It has to be something I can easily find.
EDITS FOR CLARIFICATION:
I am not planning on partaking in any illegal activities.
I do not condone the use of illegal substances and am not planning on smuggling anything anywhere.
I am not going on a hiking trip or mailing myself anywhere.
I will be staying in a tent (not a small one; a huge with with air conditioning and everything). I will be traveling for five days, returning to my current location on day 3 and traveling again on the last two days. I will not poop on the first three days (hopefully).
Clean toilets with all the expected facilities will be available to me. I am not going to poop for reasons that I wish to keep to myself.
If it gets bad, like really bad, like a-piece-of-poop-is-literally-halfway-out-my-ass bad, I will use the toilets.
Please stop asking because I am not telling anyone the reason.