The ornamental design for a drinking accessory, as shown and described.
FIG. 1 is a front perspective view of our new design of a drinking accessory;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom perspective view thereof.
The dash-dot lines in the Figures represent the boundary of the claimed design. The dash-dash lines in the Figures represent portions and environmental elements that form no part of the claimed design. None of the broken lines form part of the claimed design.