Apple hides the list of your Sign in with Apple accounts pretty deep inside Settings the settings app. Open Settings > [your name] > Password & Security > Apps Using Apple ID to see them.
If you see one that’s weird that you don’t recognize, tap on the name to see more details. You can see the date you created the account as well as the email address you used for it (whether your iCloud email or a Hide My Email forwarding address). You might see details such as the site privacy policy or terms and conditions.
Tap Stop Using Apple ID to delete this account. If you want to delete a bunch at once, go back to the list, tap Edit and tap − then Delete on all the ones you don’t need anymore.
I’d hesitate to delete many of these. They don’t cost you anything to hold on to, for one. When you delete them from Settings, you may entirely lose your access to that account, unless you have an email address connected as well.
This makes for a good to-do list if you ever leave Apple and switch to Android or Windows. While you can still sign in from other devices, you might want a more convenient way of signing in than your old Apple ID (like maybe your current email address).
This will vary for every service, but if you sign in and go to account settings, most sites will let you add an email address and password that you can use instead of Sign in with Apple.