The ornamental design for a sippybottle, as shown and described.
FIG. 1 is a perspective view of a sippy bottle showing our new design;
FIG. 2 is a front view of the sippy bottle;
FIG. 3 is a rear view of the sippy bottle;
FIG. 4 is a right side view of the sippy bottle;
FIG. 5 is a left side view of the sippy bottle;
FIG. 6 is a top view of the sippy bottle; and,
FIG. 7 is a bottom view of the sippy bottle.
The broken lines in the drawing depict portions of the beverage container that form no part of the claimed design. The dash-dot lines in the drawing represent the bounds of the claim and form no part of the claimed design.