How do you stay awake,focused?

Wandering how do students keep focused for long period of time?

I really struggle to keep focused on my study. MY brain feels foggy. I don`t want to binge on caffeine and nicotine. I start something and then zone off in to a sleepy dreamy state.

It is worse if i have to sit in a hot class room.

For example you could do push ups (e.g. 30) or sit-ups and so forth.

Hope this helps!