The best way to wash an outdoor dog bed depends on the type of bed you have. For cot-style beds, you can likely hose them off and let them dry if they use a hard plastic top or a mesh material. Other cots may have a piece of fabric you can remove and wash. Most traditional dog beds need to be washed by hand in a large tub, while others can be put in a washing machine. When buying a dog bed, the company should provide care instructions, so you know the most effective way to wash the bed.