Spa hotels are all about relaxing and unplugging from the real world, so bring clothing that is casual, loose-fitting and easy to slip in and out of. Tracksuit pants and T-shirts are great options. Bathrobes and slippers are popular spa attire, however these are usually supplied by the resort. Plan on soaking your body in the hot tub or doing a couple of fitness classes? Throw some gym wear, trainers and a swimsuit in your suitcase too. If your hotel has a restaurant, check if it has a dress code — you may need to bring something smart to wear to dinner.