Practice all kinds of short hops: Straight-on, backhand, glove side, hot potato in the hole. Focus drills on the fundamentals of quick feet, centering the ball, moving to either side, keeping your eyes on the ball.
Put your players into circles - about 6 players to a circle. Hand a ball to one player.
The players will throw a short hop to anyone in the circle. If the throw is poor, the player is out. If the throw is good and missed, the player making the fielding error is out. (Don't call the player out if it's a bad hop).
Keep going until one player is left. The players that are out should be cheering the others on. Keep working all the players until you have a team champ. Repeat the drill at all practices so that other players get a chance to de-throne the champ.
Remember that keys to becoming a good infielder are learned skills, not merely the result of natural ability.