If you work in a coffee shop and a customer complains that the coffee tastes terrible, what would you do?

make no hesitation or argument,taste the coffee yourself and replace it with the good ones,no need to risk.just one coffee,there is more,don't let go of a big opportunity just because of a single problem,because for sure,you will get more costumers.

 I would ask him to be more specific like "do you like it with more sugar?" "do you want to put more milk or creamer?" then provide what he really wanted.