Can I Bluetooth my Apple Watch to my Oticon-on hearing aids

There is an Oticon-ON app for the Apple Watch. The app works the Oticon-ON app for your iPhone. You would need to get the Oticon-ON app installed on your iPhone and hearing aids paired in Accessibility under Hearing Devices. Then you can use your Apple Watch to control your hearing aids. There is no Bluetooth connection from Oticon hearing aids to the Apple Watch.

Not directly no, however you can if you have an Oticon ConnectClip.

You do not need the Correct Clip. Install Oticon-On on your iPhone and then open the Apple Watch app on your iPhone and then install Oticon-On on your Apple Watch. You can now control your Oticon hearing aids from your Apple Watch. You do not have all the features you have on your iPhone but it works great.

I assumed the OP was wanting to stream audio from the Apple Watch to the hearing aids.

I missed that reasoning. Thanks for the correction.