OK. This will require an area normally larger than an average 2 car garage..
This is a drill our entire Men's team would do but works just as well for youth teams. It is appropriately called "The Mini Tramp Drill".
We were fortunate as our head coach was also a head coach at a local high school so we were very fortunate to have the use of the HS gym a couple nights a week.
You will need a tennis raquet, a bucket of tennis balls, a mini trampoline and as many mattresses, beanbag chairs or inflatable cushiony whatevers as you can get.
Here is what we did.
The bean bags, cushions, etc were placed all around the fron side of the tramp. The coach would be 20 or 25 ft away with the raquet and the bucket of tennis balls on a chair beside him. Another coach with a glove was on the other side of the bucket.
A player, in stocking feet with their glove on, would get on the trampoline. The player would start bouncing and shifting their weight from thr left to right foot. Small bounces and small shifts but quickly enough so that their body was constantly either goig up or down and left or right at the same time.
The coach would take a tennis ball and hit it at or near the player. The player had to catch it in the glove, dig it out and fire it to the coach with the glove. The coach started out somewhat slow and gave each player 20 shots going as quickly as reasonable. On the 2nd round, the balls came a little faster, next round - faster yet. Now, at least once or twice per person, per round the coach shot one beyond your reach either left, right or out in front and you had to dive and still catch it, ergo all those cushions. Oce in a while you even got fed a one hopper off the floor too.
We had a blast doing this and the smart Alec comments flew back and forth non-stop.
We started working out in the gym the 1st week of December. Our first tourney was always the first weeked of March. My infielders found themselves shifting their weight back and forth just like they did in the mini tramp drills in the gym. THEY ALL HAD REACTIONS LIKE A CAT!
Its a fun drill, different and it really works. Have a great season.