We claim the ornamental design for a flask with cap, as shown and described.
FIG. 1 is a perspective view of our new design for a flask with cap, shown with the cap removed;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a left side elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a perspective view of our new design for a flask with cap;
FIG. 7 is a front elevation view thereof;
FIG. 8 is a left side elevation view thereof;
FIG. 9 is a top plan view thereof; and,
FIG. 10 is a bottom plan view thereof.
The broken lines immediately adjacent solid lines represent bounds of the claimed design while all other broken lines are directed to environment and are for illustrative purposes only. The broken lines form no part of the claimed design.