Anyone with a credit card
And presumably their app?, which requires either an Apple or Google account.
I'm sure you can imagine why it might be unnecessarily complicated for a Waymo to take cash.
What reason would someone have not to have a credit or debit card? Credit cards are literally free money, as long as you pay the balance off on time
Debit card works just fine with Waymo, just like with Lyft and Uber.