I'm doing this guide because so many people are wondering how coffee works in Fast Food Simulator, so here we go:

There are 4 kinds of coffee:

1) Regular Coffee: 1 click on the Coffee button, it will fill the cup up to 70%;
2) Double Coffee: 2 clicks on the Coffee button, it will fill the cup up to 100%;
3) Coffee with milk: 1 click on the Coffee button, then you must heat up the jar with milk first(top button), after it's on 70 degrees, pour some milk in the coffee cup, 1 click equals to 15% milk;
4) Coffee with extra milk: 1 click on the Coffee button, don't forget to heat up the milk jar, and pour milk twice, it will give you 70% coffee plus 30% milk.

Hope this will help you guys! Cheers