The ornamental design for a sleeve for container, as shown and described.
FIG. 1 is a front perspective view of a sleeve for container;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left elevation view thereof, the right elevation view being a mirror image thereof;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken lines consisting of dash-dot-dash lines in the drawings depict the boundary of the claimed invention and it is understood that the claim extends to the boundary that forms no part of the claimed design.