The ornamental design for an insulating cupsleeve, as shown and described.
FIG. 1 is a top perspective view of the design of an insulating cup sleeve showing the new design;
FIG. 2 is a bottom perspective view of the insulating cup sleeve shown in FIG. 1;
FIG. 3 is a front elevation view of the insulating cup sleeve shown in FIG. 1;
FIG. 4 is a right side elevation view of the insulating cup sleeve shown in FIG. 1 (the left side elevation view of the insulating cup sleeve is a mirror image of the view shown in FIG. 4); and,
FIG. 5 is a rear elevation view of the insulating cup sleeve shown in FIG. 1.
The features shown in broken lines depict environmental subject matter only and form no part of the claimed design. The boundary lines depicted as dash-dot-dot-dash lines define the boundary of the claim design and forms no part thereof.