Have you a travel sheet in you bag or backpack? You should have one. Travel sheet is an extremely lightweight and roomy sleep sack or sleeping bag liner. It adds warmth and keep your sleeping bag clean. Thought it is called sleeping bag liner travelers can use it in hostel or hotel beds were their have doubts about hygiene of these places. It also makes a great airport/travel cover blanket. It easy to clean as it is machine washable and colorfast.
Of course these sheet are in a lot of different sizes and fabric. It can be mummy shape or rectangle, with zipper or without it, made from cotton or micro fiber.
The prices start at 15US$ and goes up to 50-60US$. I am using cheapest cotton travel sheet(like this one) and am very happy with it as it doesn’t take much space in my luggage. I am packing it right now for my trip to India.