Adding funds to another Apple ID

Buy/redeem Apple Gift cards to the account.

Apple Card  -

Gift cards redeem.   *

ASC YouTube for how to redeem an Apple Gift Card | Apple Support

Gift Card - can’t redeem.   *

App Store & iTunes Gifts - Resend *

Or if you aren't in Family Sharing.

Apple ID - Add funds to your ID      *

You are welcome. Contact iTunes Support for assistance. See the Apple Support articles below for contact information.   

iTunes Support – world wide   -

Apple Support schedule phone call     -

Billings and Subscriptions   -

Apple on Twitter