That size ball full of water is going to be really heavy. More than a few swings can start causing wrist issues. It's also not uncommon for kids to react to additional weight by pushing harder. Pushing is not the kind of movement we want to emphasize.
When conducting a hitting session, here is a list of the equipment I have with me.
* Tanner Tee
* Bow Net
* Two buckets filled with balls
* Zepp sensor that I rarely use. I do like capturing some measurements once in a while but it isn't used often.
* Set of 12 TCB wiffle balls. Again, don't use them much, but do use them. Especially if we are hitting at our house where hitting regulation balls can get us both in trouble with DW.
* A NFHS regulation size football. Yep... DD likes playing catch with a football as a warm up before pitching or hitting. Don't ask me why. But I enjoy it too, so I don't argue.
Beyond that I rarely, if ever get involved with any other items. If others find benefit in their use, I wish them the best of luck. Just not something I have much interest in.