The ornamental design for a foldablecontainer sling, as shown and described.
FIG. 1 is a perspective view showing an exemplary embodiment of my new foldable container sling design, with an exemplary container being supported therewithin;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a perspective view of an alternate position of my new foldable container sling design, namely, in a folded position.
The broken lines are for illustrative purposes only and form no part of the claimed design. Additionally, the appearance of any portion of the article between the break lines forms no part of the claimed design.