The price of coffee is very low, but the transaction fee of BTC is too high at present. The price of a transaction fee is higher than that of a cup of coffee, so it is impossible to pay coffee with BTC at present.
I don't believe that Bitcoin will qualify as payment for a coffee because Bitcoin is the slowest transaction speed of all the cryptocurrencies in the market todaY.
I believe on crypto that will being used as one of the mode of payment for some business establishments like coffee shop and fast food restaurants but it should be the fastest crypto that could transact in just aron 60 seconds or less.
Ripple, DogeCoin, Tron and other billion supply coins would be the better suit to these needs.