Sign in with Apple ID: different apps / same company > use same account?

I have an account with DoorDash and used "Sign in with Apple ID" to take advantage of the hidden email / easy login feature. DoorDash also owns Caviar (different apps, same company). Since I have the premium "DashPass" service which works on both apps I want to use the same account to login with Caviar - but I don't know how to use the same login info on a different app. When I go to "Sign in with" the Apple ID, it prompts me to create a new account. How can I bring the Apple ID-based login info from DoorDash into Caviar? Thanks!