Keeping your backpack clean does not only ensure that it looks fantastic, but also that it remains fully functional. The best way to wash a backpack is simply with water, and, if necessary, a mild soap. Lukewarm water and either scrubbing with your hands or a gentle brush should wash off most of the dirt that you accumulate while hiking. Make sure you hang-dry your backpack in a shaded place, away from any extreme sources of heat. Do check the instructions that come with your backpack for specific care instructions for your product.