There are many ways to amp up your focus before rehearsal. Some dancers meditate. Others chug a latte. A recent study found that the key to concentration could be as simple as sipping some water: People who drank three cups just before beginning a task increased their brain’s reaction time by up to 14 percent. Apparently, even being a little thirsty can distract you. So the next time you start trying to learn a tricky new phrase, fill up your water bottle. You’ll feel perkier in no time.