How to transfer money from your Apple Account to Apple cash?

The Apple Support article: Check your Apple ID balance - Check your Apple Account balance - Apple Support says:

"About unused Apple ID balance

You can't redeem or return Apple Gift Cards, App Store & iTunes Gift Cards, or unused Apple ID balance for cash, except as required by law. If your jurisdiction allows for refund of redeemed gift balances, you can contact Apple Support [ Contact - Official Apple Support ] to request a refund."

If this is about your Apple ID balance, you can not use this balance to pay for other services and content than those from Apple.