Staying Focused

I keep running into a problem where I miss questions on my practice tests mainly when my mind starts to wander and/or I start to lose focus for other reasons. Does anyone have any tips for avoiding this? Not too too worried about changing my practice test environment, but I AM worried about staying focused on test day!

Also on this vein, what do people eat the morning-of test day (and during the break) to boost energy and stay focused?

Thank you so much — seriously appreciate any and all advice on this:))