Dr. Bronners, more than just a long bathroom read on a bottle.
Before we start, let's get just get this Doctor reference out of the way...
Can you believe it's been ten years since this? My, how time flies, as does the TARDIS. And while the Doctor is probably the ultimately cosmic backpacker, here on Earth we don't get the luxury of a spaceship to keep all our wardrobe and items in. At best, it's carry on luggage or a backpack.
But there is a Doctor that I've found incredibly useful for travel, aside from our Time Lord friend.
Doctor Bronner's can be used as shower gel, bath soak, washing hair and face in a pinch, as laundry soap, etc. etc. It claims to have 18 uses, but as travel goes I care about it as shower gel, face wash, and laundry soap. I have tried it on my hair, without Doctor Bronner's follow up Hair Rinse, and found I didn't like it. But then again, apparently you're supposed to use the slightly acidic hair rinse to counteract the alkali in the soap. Without it, it makes the hair feel a bit dry and off.
It's also my favorite thing to use for cleaning my makeup brushes, so having a small bottle of this in my backpack gives me a lot of use in one product, instead of 3-4 separate ones. Space saving, good for the planet, and they also just smell really good. Peppermint, Rose, and Citrus are my three favorite, although I would suggest not using the Peppermint one on the face due to the menthol/mint oil levels in it. The Tea Tree or Rose one are better options.