The ornamental design for a cap for container, as shown and described.
FIG. 1 is a perspective view of a cap for container showing our new design with the cap sidewall in broken lines;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines in the drawings depict environmental subject matter only and form no part of the claimed design. The broken lines immediately adjacent elements shown in solid lines.