What address do I send my broken AirPod back to?

Did Apple send you a return box? If so, a pre-addressed return label is under the label that got the package to you.

As we are not Apple and do not even know where you are in the world, we have no idea of what address you use. If the label is not under the other, you need to contact Apple support. They will not see your issue in these user-to-user forums.

You would get a shipping label (with barcodes) from Apple with the address on it, and probably postage prepaid (i.e. courier of their choice). If you received a box from Apple, look under the current label for more paper documents. Else you may have received a label digitally by email (PDF to be printed by you).