Toilet paper is bulky, slow to degrade in the backcountry, and accumulates fast over 2,000 miles. The Bottle Cap Bidet replaces it with a 4 g attachment that threads onto any 28-410 bottle (Smartwater, NOBO, Lifewater) and turns your water into a concentrated cleaning stream. Because it threads externally rather than plugging into the neck, it won't pop off under squeeze pressure the way push-in bidets do. An integrated silicone gasket seals the bottle's lip cleanly. Use a dedicated trail bottle for it (and run the Cap & Tether on the bottle you drink from) and skip the toilet paper entirely.