personally, i set multiple alarms, because i have really hard time waking up. if i have to be awake by 6:50, ill set an alarm for 6, 6:30, 6:40, 6:45, and 6:50, because my main problem is just falling back asleep. also i've gotten in the habit of playing sudoku on my phone in class because it helps me listen during lectures and stuff, does anyone else do stuff like that? also i should probably explain that to my teachers so they dont think im ignoring the lesson..
Another idea for not falling back asleep is getting out of your bed. You could get 50 more minutes of high-quality sleep by putting your phone or alarm across the room so that you have to get out of bed to turn it off. Just an idea.
And yes, I’m sure your professors would appreciate your explaining the sudoku. I promise they’ve already noticed that you’re on your phone all the time, so, even if they’re grumpy about it, somewhere deep down it will help them to know that you use the sudoku to pay attention.
I knit during the sermon at church (sometimes I do cross-stitch). I used to do puzzle books when I was in university (we didn't have smart phones back then, and I couldn't afford a PDA at the time). It's all part of how you focus. Telling your teachers is a good idea, though; explain it to them so they know what's going on. (They may not fully understand; I've had difficulty explaining to people in the past, but at least they know you have a reason for what you're doing.)