The ornamental design for an insulatingsleeve for a beverage container, as shown and described.
FIG. 1 is a front elevation view of an insulating sleeve for a beverage container showing our new design;
FIG. 2 is a rear elevation view thereof;
FIG. 3 is a left side elevation view thereof.
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken lines in the figures are directed to environment forming no part of the claimed design or show portions of the insulating sleeve for a beverage container that form no part of the claimed design. In the drawings the long dash broken lines depict environmental subject matter that forms no part of the claimed design; the short dash lines depict portions of the article that form no part of the claimed design.
The shade lines in the figures show contour and do not claim surface ornamentation or treatment.