Well it depends on whether you want to invest or go cheaply. My #1 rec would be blackout honeycombs but if you're renting you obviously don't do that. When we rented a house with very sheer shades the year my DD was born I simply put blackout panels from lowes on a tension rod behind then, but that was not greatly functional (to open and close regularly). PBZk, LON have nicer blackout panels

Just bought Eclipse based on recommendations from this thread. Our old blackout curtains decomposed. Thanks to whoever recommended them. Our room is totally dark.

We have old Eclipse curtains layered over blackout cellular shades. I note that they are old because I do not think they are made as opaque now as they used to be.

We were desperate and ordered from blackoutez and they are legit. We have blackout cellular shades, but so much light was still coming in the sides. These velcro to the window frame and the room is pitch black.