The ornamental design for a magneticholder for a beverage container, as shown and described.
FIG. 1 is a front view of a magnetic holder for a beverage container;
FIG. 2 is a right side view thereof, the left side view being a mirror image;
FIG. 3 is a top view thereof with a cross shaped opening centrally located on the bottom surface;
FIG. 4 is a bottom view thereof;
FIG. 5 is a back side view thereof;
FIG. 6 is an isometric view thereof;
FIG. 7 is an isometric view thereof with a beverage container drawn in broken lines showing the magnetic holder for a beverage container in condition of use; and,
FIG. 8 is a right side view thereof with a beverage container and a magnetically attaching structure drawn in broken lines showing the magnetic holder for a beverage container in a condition of use.
The broken lines of the can and wall in FIGS. 7 and 8 are for illustrating environmental structure and form no part of the claimed design. The remaining broken lines in FIGS. 1-8 are for unclaimed portion of the claimed design.