The main objective is practicality and comfort when you're staying at a spa hotel, so loose, non-restrictive clothing is the choice of attire for most guests. While it's likely you'll spend much of your time wearing a toweling robe and slippers, these are usually supplied to guests on arrival. If you plan to use the resort's exercise and fitness facilities, pack your sports gear. Hoping to release some tension in the pool or steam room? Be sure to throw a swimsuit in your bag. Along with toiletries and other essentials, bring some extra clothes too. It's nice to have something clean and fresh to slip into after a treatment.