How can I upload Apple Watch activity rings data to my Health App or Apple Account without an iPhone?

Sorry, but you will need an iPhone to sync your Health data from the watch.

If you don't have your old phone to sync and backup, you will lose all Health data since your last watch backup.

Have a look at the related article.

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If you don't have your old iPhone or you erased it

Your Apple Watch might still be paired with your old iPhone. Use the steps below to unpair:

1. Erase your Apple Watch. 
2. Set up your new iPhone and sign in to iCloud. If you've already set up and signed in, skip this step.
3. Open the Apple Watch app on your new iPhone, then pair your watch with your new iPhone.
4. Try to restore from a backup. Make sure that your iPhone and Apple Watch are up to date; if they're not, you might not see your backup in the list. You will lose Activity, Workouts, or settings on your watch that changed between the last backup and now. If you use iCloud in iOS 11 and later, Health and Activity data is stored in iCloud and automatically kept up to date on devices where you're signed in to the same Apple Account. 

• • If you’re asked to restore from a watch backup, select the most recent backup. 
  • If you don't have a backup, you need to set up your Apple Watch as new. 

5 . Follow the onscreen steps to finish setting up.

6 . Start using your Apple Watch with your new iPhone. You might need to wait a few days for all your iCloud data to appear.

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How to pair your Apple Watch with a new iPhone - Apple Support