Staying awake...

I am having a really hard time staying awake during the test. I zone out around question 13-15, and come back by 20, but does anyone have tips to remain more alert? I'm not a caffeine person but maybe i need to become one. it just really messes with my sleep so i try to avoid it. I know that it's my biggest problem--i'm like -2/3 on each section and it's always the ones where i'm tired.