Apple Watch Trade-in.

See the 'Before you ship your Apple Watch' section in:

How to prepare your iPhone, Apple Watch, or Android for trade-in - Apple Support

where it says "Remove the band from your Apple Watch. If it is included in the box, it will be recycled and cannot be returned to you."

See the FAQ section in:

Apple Trade In - Apple

• Do I have to include accessories like chargers and cables?
• No, you do not need to include accessories. If you choose to include any, we will recycle them for you.