The ornamental design for a beveragebag, as shown and described.
FIG. 1 is a perspective view of a beverage bag showing our new design;
FIG. 2 is a perspective view thereof, showing the bag in an expanded condition;
FIG. 3 is a left side view thereof, with the right side view being the mirror image of the left side view;
FIG. 4 is a left side view thereof, with the bag in an expanded condition and with the right side view of the expanded bag being the mirror image of the expanded left side view