I am not looking for a workaround; I specifically want to capture the notion of seasoning to one’s own taste”, But for coffee/tea. I have never encountered “season” in any other context.

If “fat” or “sweeten” is an option, it doesn’t seem quite right for, say, milk.

Another alternative is a generic word like “prepare”, “do”, “handle” all of which vaguely capture the task of making coffee preparation, but it feels they get away with it only by making it implicit.