The ornamental design for a backpackwaterspraytank, as shown and described.
FIG. 1 is a perspective view of a new and ornamental design for a backpack water spray tank;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a first side elevation view thereof;
FIG. 5 is a second side elevation view thereof;
FIG. 6 is top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view of a person wearing the backpack water spray tank with the person shown in phantom lines for environmental purposes only and forming no part of the claimed invention.
The broken lines shown on portions of the backpack water spray tank represent stitching.