Last year I was pulling off all nighters, so yeah I didn't "waste time" by eating any meals (just lots of snacks), showered like once every week, managed like an hours sleep each day
Also because I was told it was important to be hydrated during exam, I was drinking tons of water during the day and, you know what that leads to..
This year I've just been opposite. Totally chilled, getting as much sleep as I can. But I think it's mainly the people who haven't revised enough who pull off these stunts