Hi Maddison, 

The best drill for this would be to have reaction balls, simply get your players to pair up - one player would be the worker, the other the feeder. The worker would be on their toes demonstrating fast feet so they are ready to react to the ball. At any time the feeder will bounce the ball and the worker must react. The feeder should mix up the difficulty of their bounces depending on the ability of the worker. 

Another good drill to get your players aware of what is around them is peripheral vision.. This is a good drill to get your players focusing on multiple stimulus and develop their wider awareness of the court. 

Hope this helps.