The ornamental design for a cupholder, as shown and described.
FIG. 1 is a perspective view of the cup holder according to the present invention.
FIG. 2 is a top view of the cup holder as illustrated in FIG. 1.
FIG. 3 is a side view of the cup holder as illustrated in FIG. 1, the other side views being identical; and,
FIG. 4 is a bottom view of the cup holder as illustrated in FIG. 1.
The broken line showing of the hole in the bottom of the cup holder, visible in FIGS. 2 and 4, is for illustrative purposes only and forms no part of the claimed design.