During the part of The Hateful Eight that showed what happened before, I missed the part that explained why the coffee tasted so awful. What did I miss?
There's nothing explicitly stated about the coffee in the movie. However, the fact that it was so bad is a clue to the fact that even though the Mexican fellow was supposedly working in the haberdashery for the past few months, he still doesn't know how to properly make a pot of coffee, thus revealing that he did not in fact work there at all. Of course you'd have to be extremely observant to draw this conclusion based on that alone, so it's more of a 20/20 hindsight type scenario, or foreshadowing that is only revealed as significant once you know the whole story.
Actually, Minnie stated "Stagecoach drivers like it (coffee), passengers not so much" when the coffee was ready and her husband, Sweet Dave, claimed "best coffee on the mountain". Since John was indeed a passenger and he prob has not gotten used to Minnie's Hot, Strong and its *good flavor.
In reality, good* is subjective to a person's taste. That's why there are Breakfast Blend, Medium Roast, Dark Roast, not to mention black or with cream & sugar, etc.