I wake up feeling slightly groggy after taking it around 7 hours before, but as soon as I get to moving around and drink a cup of coffee, I am golden, so I would so no to the sleepiness, but could be different for each person.
This product contains diphenhydramine which is the active ingredient in Benadryl. A known side effect that this product is advertising for, is sleepiness. Therefore, you are taking an allergy medication to make you feel sleepy. Some people metabolize this drug more slowly than others and may feel "hungover" or sleepy the next day. Other people will not feel sleepy at all and feel more energized after taking the medication.