We backpackers are a funny group. We admit to hygiene practices that aren't really discussed or tolerated in civilized society, like equating a dip in a lake to one-half of a proper shower, or recycling undergarments for up to a week or more at a time.
But it's not that we always choose these unkempt routes for ourselves. Sometimes laundromats are in short supply, or there's so much to do in a place that taking a few hours to wash clothes is low on the list of priorities. Whatever the reason, travelers are known to be a smelly bunch.
Personally, I hate the thought of being "that guy" in the train compartment (or wherever), which is why I make a strong effort to set up a laundry station almost as soon as I check in at a hostel. The supplies are fairly cheap and amount to no more than a soda can of space in a backpack, and the benefit of not having to wait for clothes to dry allows the travel hacker extra time at the beach, in the art museum, or otherwise out on the town. As a bonus, it's also a great way to make friends in your hostel dorm—who knows? Maybe you'll score a free drink in a clothesline-for-beer barter.
Here's what you'll need for your improvised laundry station, getting you that much closer to traveling fresh:
5-liter (minimum) collapsible bucket: These steep-walled folding buckets are the size of a hockey puck when minimized, and they make an excellent washbasin for garments. If you can snag the version that has handles, hang it on a faucet to keep water from spilling over the sides.
Utility cord or webbing: You'll tie this to two stationary points in your room as a makeshift clothesline. Your best bet on keeping this line taut is an anchor bend or a buntline hitch, as they're low-profile and get stronger with tension.
Concentrated laundry soap: This can be picked up almost anywhere, so don't pack it away into your checked luggage. Pick up a small bottle on arrival, and use only as much as needed—only a tablespoon or two is enough for five liters of water. Any more, and people will pick up on your alpine meadow-scented pantalones from several blocks away.
Bleach pen: Use this for all of your spaghetti sauce stains, or better: bring a blank, dark-colored t-shirt with you, and have everyone you meet along the way write a message in bleach on the shirt. It's a fun, quirky way to catalogue the wonderful people you encounter.