Can concentrated lemon help reduce fatigue and sleepiness?

Maybe a better way. Experts suggest the following measures for reducing fatigue and recharging energy: 1) Add some exercise; 2) Treat sleep troubles (as warranted: cognitive therapy, address sleep apnea if present; some benefit from yoga, tai chi, meditation); 3) Manage pain (if present, identify what makes pain worse & what eases it). Ref. ArthritisToday2015.
Not to any degree. Citric acid does not decrease fatigue. It certainly may not hurt to try it, but is unlikely to improve your alertness to any degree. The smell of lemon does make some people feel more alert for a few seconds, but does not increase energy levels. Your best bet is to get at least 7 hours of uninterrupted sleep per night.
Never heard of this. I never heard this before. I doubt it would really make a difference.