Not all bags are created equal, and when it comes to freezer-safe choices, the best (and most sustainable) reusable silicone-style bags are compared to disposable bags. Aside from being a convenient, machine-washable option, "you can also reheat the entire bag in a saucepan of hot water," suggests Moon.
Freezer-specific plastic bags are also an option – and better than traditional sandwich bags. These are made of thicker and more stable plastic, which prevents them from leaking or becoming brittle. Since liquids expand as they cool, leave an inch or two on the top of the bag (this goes for almost any soup-friendly container you choose). Buying quality freezer bags from a reliable brand that you trust is always a good choice.
A quick tip: If you want to prevent the freezer from burning, try to force as much air out of your zippered freezer bags as possible (although this is certainly not necessary, a vacuum sealer can come in handy). Then freeze your bags flat or store them upright like books to maximize freezer space.