I'm certainly not the first to recommend this but it's worth restating.
As soon as you wake up, drink a 16-24oz glass of warm water possibly with the juice of a freshly squeeze lemon and/or a splash of apple cider vinegar but it's just fine on its own.
First and foremost, this is a great way to get more water in your system. Do it first thing and make it a habit.
Second, you presumably haven't had anything to drink for 6-10 hours. Dehydration makes us do silly things. Don't be silly. Avoid dehydration induced idiocy and drink up!