How to share fitness activity with perfect strangers
Sharing fitness activity among friends and family is covered in good detail here:
Share your Activity and compete with friends with your Apple Watch - Apple Support
However this can be a lot of fun with any other people around the globe as well. It is actually pretty easy to find other like minded activity enthusiasts on the popular social media platforms.
The invitation and connection is made by Apple ID, which is often quite cryptic piece of data.
However you can also tag and label your new friend in a more meaningful and nicer way. Here's how.
In the Fitness app, under Sharing, tap here to add a new fitness friend:
Enter the given email address (Apple ID) and tap Send. Sometimes two taps are needed:
Once the invitation is accepted and sharing has started, start a quick chat.
Drop down the arrow and then tap Info :
Then tap Info one more time and now a new contact can be created.
Note that only the first name matters, as far as the Fitness app goes. You can also attach a country flag or some other emoji to the name, helping to remember who is who and where they hail from.
Finally, here the scope what data actually gets shared during Activity Sharing:
Activity Sharing & Privacy - Apple Support