The best container for freezing soup in is a regular plastic freezer safe food storage container.
Most food storage containers are safe for freezing food in and I've done it a lot of times.
I just use those regular food storage containers that are made of plastic and they have those lids that seal on top of them.
I just put the soup in the plastic food container and then seal it with the plastic food storage containers lid.
Then I mark the date I froze it and then place it in the freezer.
Then when I want to thaw the soup out I just remove the lid and defrost the frozen soup in the microwave.
You can also freeze soup in some freezer bags or Ziploc bags as well.
I've done both and never had any issues.
You can also buy freezer food storage containers that are made to stand up to the freezing temperatures but I've never had any regular plastic food storage containers crack or break and I've been freezing soup and other foods in those containers for 10 years now.