You need sleep to help your brain work the way it should, but too much can make you feel foggy, too. Aim for 7 to 9 hours. To get good rest at bedtime, you may want to avoid caffeine and alcohol after lunch or right before bedtime and keep the computer and smartphone out of your bedroom. It also can help to get to bed and wake up at the same time every day. Talk to your doctor if you think your brain fog might be caused by a sleep disorder like apnea, insomnia, or narcolepsy.