You can make very good plant pots from used plastic milk cartons. Cut off the bottom part of a used plastic bottle - the square ones are particularly useful - drill a few holes in the bottom and you have a useful pot. The plastic will cut easily with a pair of small sharp scissores. You can vary the size of the pot by changing the height that you cut off the bottle. But be sure that you can get your drill inside to make the holes. If you use a hand drill you need room to turn the handle.
The rest of the bottle can be put in the recycling or you can use the spout end to direct water at the roots of a plant by pushing the spout into the ground next to your plant and pouring water into the up-turned bottle.