The ornamental design for an expandabledrinkingflask, as shown and described.
FIG. 1 is a front, top and right perspective of an expandable drinking flask showing my new design;
FIG. 2 is a rear, bottom and right perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a left side elevation view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The drinking flask is shown with a symbolic break in its height. The appearance of any portion of the article within the broken lines forms no part of the claimed design. The broken line showing of a lid is for the purpose of illustrating portions of the flask and forms no part of the claimed design.