The ornamental design for a baseballbatswingexerciser, as shown and described.
FIG. 1 is a top perspective view of a baseball bat swing exerciser showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right-side elevation view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a top plan view thereof.
The broken lines in FIGS. 1-7 are included for the purposes of illustrating the portions of the baseball bat swing exerciser that form no part of the claimed design.