I am always happy to find a way to reuse stuff. Not so I can feel righteous about recycling or whatever. But rather so I don’t have to buy more crap. I am using plastic bottles to cover early plantings (seedling of peppers and eggplant at the moment).
Just cut the top of the bottle of and put it upside-down in the soil–twist it into the ground so it doesn’t blow around if it gets windy.
If it’s not too hot, leave them on for a day or so to acclimate seedlings. You want plants to harden up, so don’t keep doing this. During this time, keep a close eye on the lows, and cover as necessary.