Apple Watch Trade-in.

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.

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."