We claim the ornamental design for a coffee machine, as shown and described.
FIG. 1 is a front perspective view of a coffee machine showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is an exploded view thereof in which the container feature is shown in a removed position and the nozzle feature is moved to an alternate position; and,
FIG. 9 is another exploded view thereof in which the container feature is shown in a removed position and the nozzle feature is moved to another alternate position.
The broken lines in the figures depict portions of the coffee machine which form no part of the claimed design.