The ornamental design for a drinking vessel, as shown and described.
FIG. 1 illustrates a perspective view of a drinking vessel employing the ornamental design in accordance with the invention;
FIG. 2 illustrates a side elevation view of the drinking vessel of FIG. 1 (each side being the same as that shown with the exception of the position of the handle);
FIG. 3 illustrates a top view of the drinking vessel of FIG. 1; and,
FIG. 4 illustrates a bottom view of the drinking vessel of FIG. 1.