Can eating salt wake you up?

Yes it can. Driving long hours as a professional driver I often had to resort to salty chips or sunflower seeds to get back my alertness for few extra hours. For some reason it works. It can give you 3-4 hours of alertness after you thought you have to stop for a nap, however, after that no amount of salt will keep you awake. Use it for emergency, don't make it a habit.