What I found help immensely with regaining my focus and mental clarity after coming off caffeine, and before that methamphetamine 4 days out of 7 for nearly a year, is taking a multi B vitamin plus 1000mcg methylcobalamin (also known as 'Activated B12') sublingually, and 200mg B6 once or twice a day, along with eating fewer sweet things and more protein and raw fats (butter and coconut oil). Plus chiropractic / osteopathic adjustments to deal with my crooked postural habits.
I also find Liquorice root as strong decoction immensely restorative.
That's what has worked for me. N=1 and all that.
Full disclosure: I hold a Diploma in Western Herbal Medicine and an Advanced Diploma in Clinical Nutrition. For what it's worth.