If you choose the Hide My Email option when signing in to an application it will create a random generated email address instead of your Apple ID when creating the account. You can find more information on this feature here: Hide My Email for Sign in with Apple
If you'd like to turn that off and just use your regular Apple ID to sign into an application you'll want to use the steps found here: Manage the apps you use with Sign in with Apple
Stop Using your Apple ID with an app
1) Navigate to Settings > [your name] at the top > Password & Security.
2) Select Apps Using Apple ID.
3) Select the application you'd like to change the sign in for.
4) Select Stop Using Apple ID.
After doing this, the next time you use the application it will prompt you to create a new account. You can then choose to use your Apple ID, or set it up with another email account.
How do I turn off the hide my e-mail feat… - Apple Community