This is a method to re use plastic soda bottles as greenhouse. I did it last winter, and I was able to keep some plants during the winter time with no problems. Of course it is not going to be useful in snowy places, but I will help in areas with mild winters.
Step 1: Step 1: Cut at Least 2 Plastic Soda Bottles As Show in the Figure
Cut the bottles a bit over the middle point. Be careful and do not hurt yourself.
Step 2: Step 2: Get the Planter Ready
Take the top part of the bottle, turn it upside down, remove the cap and put some shred old T-shirt (or any other old fabric) on its place. This will allow for extra water to drip down to the other part of the bottle and also act as an small reservoir in case you forget to water your plant.
Step 3: Step 3: Put You Plant in the Botle
Now, you can put your plant in the plastic bottle pot. You can see some of my old plants on the pictures.
Step 4: Step 4: Create the Greenhouse
Now, in order to create the greenhouse, you only need to take the top part of another plastic soda bottle and cover your plant with it. I prefer to use the same size bottles because they fit tight. However, you could use a small one. You can open use the cap of the second bottle to control the humidity in your greenhouse (although in my experience you don't need to open it at all). You can add some water in the bottom part (of the first bottle), if you notice that the plant needs some watering (also, in my experience, not very often).
I hope you like it, use it and improve it !