The ornamental design for a sandal upper, as shown and described.
FIG. 1 is a perspective view of a sandal upper showing my new design;
FIG. 2 is a left side elevation view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is an enlarged front perspective view thereof;
FIG. 5 is an enlarged rear perspective view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines applied to the sandal upper in FIGS. 1-6 represent claimed stitching.
Broken lines in or showing the sole of the sandal in FIGS. 1-7 are for environmental purposes only and form no part of the claimed design. The claimed design does not include any part of the sole.