How to keep a rented house on Top floor (11th floor) sun and heat proof during extreme summer in India, If I close the windows it became like a furnace if I keep the windows open the house will heated up with extreme heat waves. P.S the options have to be cheaper and since its a rented house with out doing any changes in the physical attribute to the house and I don't have access to the roof top (society rules).
Make a second roof to shade the roof... Cover windows and possibly walls with UV reflective film... But as changes are not permitted then about the only thing you could consider cheaply is a Zeer Pot. This can be hung in the room and evaporating water helps cooling.
Add awnings or exterior shutters to the windows. If not allowed, then hang an exterior "curtain" over each window, longer than the window. Then open each window slightly for a small breeze. In my top-floor suite I have a large west facing wall that is painted dark brown. On the inside I covered the wall with 1-inch rigid foam using spacer strips. It reduces the interior wall temp a few degrees.