So what's the best coin to buy a cup of Coffee with? Transaction cost must not be expensive and the transaction must complete before the Coffee gets cold... 
I think if you want to sell coffee with a payment method using cryptocurrency, then it's not very effective because you need time for the transaction to be completed and of course the transaction has costs, so people prefer to pay using money instead of using cryptocurrency, but in my opinion cryptocurrency is more suitable for use as an international transaction or online shop.