Potentially one of my lifetime best investments. Not just a much better night's sleep, but also great for being able to nap/chill during the day or watch a movie (especially if you have a projector setup).
While evaluating and installing better options from e.g. blinds.com or Home Depot, I used cellular blackout blinds and opted to get a system where they can be lowered from the top as well as raised from the bottom — I highly recommend that option in order to be able to bring light into your space while maintaining privacy or perhaps minimizing your own distractions.
I've often used temporary paper substitutes which are maybe even inconveniently durable (it took a long time for me to pull the trigger on my first set of real blackout blinds 😬)
Fun fact: in Germany, every window has a metal blind that rolls down the exterior of the building, a bit like a garage door, blocking out all light, and a fair amount of sound. It's so convenient. I’m confident the whole country is getting higher quality sleep, and it’s also a useful tool for temperature control.
(Generally their overall window/door tech is quite impressive).
At home I currently have a cornice (actually a pelmet) to block the sun from coming up above my curtains, as well as full length blackout curtains that are attached to the walls (I looked at lots of options including magnetic strips from a Magnetic screen door, but ultimately just used pushpins along the edges of my blackout curtains, which are a layer backing my regular curtains).
It’s bougie (though there are great sales if you’re patient) but such a treat to add a little robot that silently opens the curtains in the morning (in stages for gentle wakeup if you want) and closes them again at night (or earlier in the summer if you’re trying to control the heat).
You can also try to block the light from your bed specifically with a 4-poster bed or a bunk bed (my favorites have a larger bed on the bottom and a smaller bed up top for sitting comfortably on the edge of the bottom bunk). The world has also started embracing sleep pod technology with lots of options for tents that fit over your bed (search Amazon for “bed tent”). But I would recommend some sort of ventilation if you go this general route—I already use a Fan when I sleep, usually just in my bedroom, but there are fans with soft fabric blades which are a great option for bed-forts specifically. ⛺️
For quick trips, I use Eye mask, and for longer stays, I have a set of blackout curtains that suction onto the window.