All small businesses have a phone these days.
They simply need a wallet type app to be able to set the price of the coffee or other goods, perhaps as an instand fiat to crypto equivalent, at which point payment is made, perhaps using something like the "bump" app that allows transfer of pictures etc.
If the mass population move to an alternate 'currency' the banking cartel don't have customers & will fail.
https://cryptodaily.co.uk/2018/12/why-we-will-see-an-increase-in-crypto-payments-this-year