One of the drills I use with my younger players, ages 7-8 years, is something I started with my oldest son when he was that age.   He had trouble “keeping his eyes on the ball”, and wouldn’t watch the ball all the way into the hitting zone.

Eye on the Ball Drill
The emphasis of the drill is hitting a baseball.
He was able to catch sight of the ball as it left my hand, however he would either ” look away” or his eyes would track elsewhere.

I start by using a tennis ball, and after having the player take a batting stance, I would have him “track” the ball all the way through the hitting zone, and physically turn his head with the ball.   After several attempts, I then have him track the ball just before, but this time he would take his stride and hip turn, and using his back hand ( left in his case ) to try to ” catch ” the ball.

In most cases the ball simply hit his hand, however he very quickly was able to both   “track” the ball into the hitting zone, and move his hands to the ball regardless of where the ball passed through the zone.   From there, we worked on only “catching” balls which were in the strike zone, and “holding” on balls out of the zone.

After this drill, we switch back to a regular hitting drill, and in no time at all the reaction time, recognition of balls out of the strike zone, and proper bat positions on balls in different areas improve immediately.   I use this drill with my 7-8 year olds in coach pitch.