Can you use ApplePay to buy crypto currency?

Yes, you can. It's possible to buy Bitcoins with Apple Pay or any other non-conventional payment method from Local Bitcoin Exchange or Paxful Exchange. You can forund out about these methods here https://cryptolinks.com/cryptocurrency-exchange

Apple Pay uses the third party credit card you assigned to your iOS device. If you want to waste your real money on garbage that gains and loses hundreds, or thousands of dollars of value at the drop of a hat, go right ahead.