The ornamental design for a ski exercising apparatus, as shown and described.
FIG. 1 is a front view of a ski exercising apparatus;
FIG. 2 is a rear view of the ski exercising apparatus;
FIG. 3 shows the top view of the ski exercising apparatus;
FIG. 4 shows the bottom view of the ski exercising apparatus;
FIG. 5 is a left side view of the ski exercising apparatus;
FIG. 6 is a right side view of the ski exercising apparatus; and,
FIG. 7 is a perspective view of the ski exercising apparatus.
The broken line showing of the reinforcing framework of FIG. 4 is for the purpose of illustrating portions of the ski exercising apparatus and forms no part of the claimed design.