Nothing.
AAMOF, I've more or less sworn off caffeine. Why, you might ask?
I am, by first profession, a musician. I picked up the computer thing after that career (partially) ended.
When I was still a HS music teacher, one morning I walked into band rehearsal (first hour), and started the warm up scales.
It sounded terrible, and it shouldn't have, because I was blessed with a fairly smart and well-trained small ensemble of HS musicians. Hearing garbage coming from in front of me, I checked trombone slide positions as we ran up and down the scales and warm-ups. All pretty much OK (one not-so-bright kid missed Ab a time or two, but otherwise, no problems visible).
I said nothing to the kids, and led them into the contest pieces (late Feb./early March; if you ever did this in the USA and remember, that's what you're really working hard on at that time of year). They sounded awful, too. We plugged away, but I couldn't stop them to say much because most every note/chord sounded off, and I couldn't tell how nor why.
Rehearsal period over, I had three girls step into the office --- my "power trio" from chorus; every one of them had made "All-District" the previous year. I'd heard their pieces last week, and they were good. How did it sound? Awful!
After school I went to see an "ears/eyes/nose/throat" doc. What did he have to say? "Welcome to the ranks of normal people. Hearing accurate musical pitches requires good high frequency hearing, and as we age, we all lose some of that . . ."
Well, I thought as I left --- B.S! I can hear the notes of the top of the piano, or the piccolo, it's just that they suck today. F-sharp doesn't sound like F-sharp, E Major Seven sounds like a train whistle in a wind tunnel, melodies sound like random bleeps from a Nintendo, and harmony doesn't exist anymore because nothing sounds consonant any longer . . .
That night, I suffered, and I do mean suffered, much more than usual as my wife's family rehearsed their "Southern Gospel" music. I'm not a "Southern Gospel" fan on my best days, and that night it sounded like the place its supposed to warn you away from . . .
I suffered another day at school and afterwards went to the audiology center and the biggest hospital in the area.
30 minutes later, with hearing tests completed (freaky to be in a really sound-proof environment), I'm going over a long, long list of "medical history" type questions with the audiologist. For a while there, it got interesting:
"Syphilis"? --- No.
"Gonorrhea"? --- NO.
"Do you drink much coffee"? No . . . why?
"Well, too much caffeine causes swelling and fluid retention in various bodily tissues, including the inner ear . . ."
Boom. I had a daily six to 10 Coke® habit, and loved to have tea when I got home.
Apparently, caffeine-induced distention of the cochlea caused many of my aural nerve endings to be "displaced" and my brain was having trouble processing the vibrations accurately since they were hitting different endings than usual...two weeks on water and Sprite and things began to get back to normal, and we actually had a decent contest season. I probably have about 95% or more of my "pitch sense" and musical confidence back.
In retrospect, I think maybe God was telling me that I wasn't His only gift to the musical world. But it was definitely caffeine that caused the actual problem . . .
So, if I need to stay awake, it's willpower, or nothing . . . .
