Inform your tour leader first, when you are sick. The word is cotton, and not even heavy blends with synthetics will do. Regular jeans are to warm. A very light hat and sunglasses are necessary for protection against the hot sun. Remember, your clothing does not only have to protect you from the hot sun, but you are visiting an Islamic country.
Improper clothing is percieved as a cultural insult, which gives the entire group a bad reputation.
However, bring your swimsuit and a cover-up to get to the swimming pool, as you will have to pass through the hotel. The pools are wonderful. For the dinner hour we usually are a little more dressy than on the road, so, do not dress in T-shirts and jogging outfits for dinner. Clean skirts and blouses are acceptable. Use lightweight, durable luggage.