I only take my ADHD stimulant when I have to get school work done or I have to go in to my job. When I am off the drug, I am the opposite of lethargic. I feel very upbeat usually and hyper (but then again, I'm combined type ADHD). I can go 3-4 days before I start feeling withdrawal symptoms.

Honestly, if I am starting to feel the effects of not having a stimulant in my system, I will eat some sugary food. I'm not a huge fan of caffeine but I'm sure that it could do the trick as well. A caffeinated drink or a candy bar is not nearly the amount of stimulation as an ADHD pill but it's possible that having something like that might ease your symptoms during your medication holiday.