The ornamental design for an octagonalbottle, as shown and described.
FIG. 1 is a top perspective view of an octagonal bottle according to the present invention.
FIG. 2 is a bottom perspective view of the octagonal bottle of FIG. 1.
FIG. 3 is a front view of the octagonal bottle of FIG. 1, the rear view, left view, and right view being mirror images of FIG. 3 excluding the unclaimed thread element;
FIG. 4 is a top view of the octagonal bottle of FIG. 1; and,
FIG. 5 is a bottom view of the octagonal bottle of FIG. 1.
The broken lines shown in the drawings illustrate environmental subject matter only and form no part of the claimed design.