I claim the ornamental design for a sheet for vehicle seats, as shown and described.
FIG. 1 is a surface view of a sheet for vehicle seats according to the design claimed;
FIG. 2 is a reference view of FIG. 1; and,
FIG. 3 is an enlarged detail view of the area in FIG. 1 which is circumscribed in the reference view.
The broken line perimeter surrounding FIG. 1 represents the boundaries of the claim and forms no part thereof. The dot dash dot broken lines circumscribing the detail form no part of the claimed design. The thickness and rear of the sheet for vehicle seats form no part of the claimed design.