Modafinil
"I'm a 27 year old male and work 80-90 hours/week. I found that I crash after 3-5 hours if I don't prepare my body with proper nutrients before taking a 100mg dose. Eating a solid meal before, and healthy snacking during has given me great results. Wakefulness, alert, no jitters, and no crash. I also have at least 2 cups of coffee throughout the day to keep it consistent. Positive results if you use it correctly."