The transit hotel is available for booking, although prices start at a minimum 6-hour block, if I remember correctly. You can have a lie down and a shower, and make use of the gym as well. In T1, there is also a swimming pool.

The next option would be to use one of the lounges where you can pay money to get into. It gets you a shower, a slightly nicer place to sit, with some limited food and beverages options. Some lounges may offer massages, and Some also have nap rooms. These services can be paid for as well.