In San Francisco, we now have a law that restaurants cannot use styrofoam for take out and leftover containers. Many are using recyclable/reusable plastic and even compostable containers. That’s great, for sure, but what is even better is not having to take any new container at all.
You can bring your own leftover containers (preferably glass or metal, but reusable plastic is ok too) when you head out to a restaurant and put your leftovers away in them. It saves the physical resources of the containers you would have used and the money resources of the restaurant (many of which operate on a very slim margin). You’ll also be modeling green living for other diners!