Unity has integrated a 2d physics solution that is very similar to their 3d solution. It has different strengths/weaknesses relative to the 3d solution.
Another option is simply using 3d physics volumes with your 2d sprites if you need features of the 3d physics systems. This works fine and you can constrain objects to a plane/rotation axis as needed.
Another option is simply using 3d physics volumes with your 2d sprites if you need features of the 3d physics systems. This works fine and you can constrain objects to a plane/rotation axis as needed.