Yeah, I do not miss rentals.

We fitted that reflective window film all around our place. It's dead cheap and passively cools the place by blocking UV and some other light. The ones that stick from "static cling" should peel off cleanly if you're worried about your landlord complaining? It made our place from uninhabitable to tolerable in an evening.

Also for anyone that's looking, if you're going for a portable air con, always go for one with two hoses! You can modify some to make them way cooler too.