I claim the ornamental design for a fast food bag with external napkin compartment, as shown and described.
FIG. 1 is a front perspective view of the fast food bag with external napkin compartment, showing my new design, in the folded condition with the external napkin compartment in the closed position;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a left side plan view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a front perspective view of the fast food bag with external napkin compartment, showing my new design, in the unfolded condition with the external napkin compartment in the open position.