The ornamental design for a sandvehicle, as shown and described.
FIG. 1 is a perspective view of a sand vehicle showing my design;
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 fragmented cross-hatching shown on the leg rest, seat and backrest is understood to represent fabric which would be continuous throughout the implied areas.