PET (Polyethylene Terephthalate)
It depends. Some milk bottles are glass, some are plastic etc.
plastic is cheaper than some other materials and it keeps the fluid in it fresh
In many cases, plastic has replaced glass in bottles and building materials. Plastic has replaced some metal on cars.
Plastic bottles that are empty may be harder to find in bulk. Most companies make their own bottles with their own materials. However you can buy just some regular water and drain it and use the bottles.
for drinking with a liquid thing like a water
Plastic bottles are mostly recyclable
Most plastic bottles are a mix of new and recycled plastic.
they are better for enviroment because they last longer than plastic and are not thrown away as aften as plastic bottles
Most recycled plastic bottles are recycled into... plastic bottles, especially PET plastic, the one with the Number 1 in the triangle. Other kinds of plastic bottles can be again made into similar plastic bottles, or they can be "downcycled", that is, combined with other plastics to make things like garbage bins and garden furniture.
Well, plastic is made from used plastic bottles so I guess that they want to recycle.
Milk bottles have clouded plastic because that type of plastic is stronger than others.
Plastic bottles are produced by blow molding.