The ornamental design for a waterbottlefilter, as shown and described.
FIG. 1 is a top perspective view of a water bottle filter showing my new design;
FIG. 2 is a front elevational view thereof, the rear elevational view, right side elevational view and left side elevational view being identical thereto;
FIG. 3 is a top plan view thereof; and,
FIG. 4 is a bottom plan view thereof.
The broken lines shown in FIGS. 1 and 3-4 form no part of the claimed design.