The main goal is practicality and comfort when you're at a spa hotel, so loose-fitting, casual clothing is what most guests generally wear. While you'll likely spend a good deal of your time wearing a fluffy robe and slippers, these are often waiting for guests when they check in. If you plan to use the fitness facilities, pack your sportswear. Hoping to kick back and relax in the pool or hot tub? Don't forget to throw a swimsuit in your bag. Along with toiletries and other personal belongings, bring extra clothing too. It's always great to have something dry and clean to put on after a treatment.