Due to stressful circumstances, I got 2.5 hours interrupted sleep last night (on a hard floor with my head on a beanbag).
As a student I did this in the knowledge I could nap during the day, but I've no idea how to go to my 9-5 job and stay alert.
I don't like Redbull/energy drinks, and I don't have ProPlus.
Don't drink caffeine. You'll be energetic for a while and then you'll just have one almighty crash. (Made that mistake at college). Eat some crisps and hope you don't fall asleep! Tiredness comes in waves, so if you do an all nighter, you'll feel like hell at about 7am, but then you'll feel totally fine at about 10am (Just an example), then you'll become tired again later on. Just fight through the tiredness waves with high carb/sugary foods.
Just keep working. Eat and drink plenty to keep your energy levels up. A half hour nap during the day can help - longer than that tends to be counterproductive, so set an alarm. Believe me, when you have no alternative it's possible to survive on about a couple of hours' sleep for several days, although obviously your decision making and coordination will suffer a bit. The joys of being a junior doctor! (yes it does still happen in some specialties - the NHS just has to fiddle what it counts as work - just because I'm in the hospital at 3am seeing patients doesn't mean I'm counted as 'working' from the point of view of pay or the European working time directive!)