It is worth noting that caffeine is not the only chemical that can be put in solution and used with a nasal spray bottle. I had a friend who weaned himself off a terrible (Todd Todd Todd Todd Todd T. Squirrel terrible) cocaine addiction with a nasal sprayer filled with coke and saline.
It was super convenient because he already had crazy nasal problems which, compounded by the cocaine abuse, meant he had to use nasal spray all the time anyway. He used the "reduction cure" ala Junky and was able to kick the habit and graduate college. It worked better for him than rehab ever did and was a happy medium between the assholery of being a cokehead and the fuckwaddery of being in withdrawl.