Have you found any supplements or alternatives that increase focus but did not impact your sleep quality?
Sadly, I have no alternative recommendations. Everything that claims to increase "focus", also appears to impact my sleep.
I am _hugely_ sensitive to caffeine and feel a buzz even from decaf. It ruins my sleep in a similar way to what a couple people in this thread describe.
I take 10mg of instant-release Ritalin at 7AM each day, and it allows me to focus and deliver. It wears off by around 2-3PM, and I sleep like a rock most nights.
There are downsides as well: once it wears off, it leaves you mentally drained until you've slept. Also, there's a potential for building a tolerance, as well as potential for addiction. I've been lucky in both cases so far, but ymmv.
Aerobic exercise (preferably outdoors) is the one thing that works with mostly positive side effects.
Seriously.
I panic if I run out