The ornamental design for a bottletether, as shown and described.
FIG. 1 is a front perspective view of my new design for a bottle tether, showing an attachment loop coupled by a snap buckle to a tethered bottle retaining loop;
FIG. 2 is a right side view of the article shown in FIG. 1;
FIG. 3 is a left side view of the article shown in FIG. 1;
FIG. 4 is a top view of the article shown in FIG. 1;
FIG. 5 is a bottom view of the article shown in FIG. 1;
FIG. 6 is a perspective view showing the article in FIG. 1 in an intended environment of use (attached to the handlebar depicted in phantom line); and,
FIG. 7 shows the bottle tether in FIG. 6 detached from its attachment loop by its detachable snap buckle to be separately carried by a user (depicted in phantom line).