There both used for sleep so, yes, prepare for bed.
The problem is two fold. First you are dehydrated. You should drink 4 8oz. glasses of water immediately before you go to bed. Second, your skin is not being moisturised properly. You should rub Vaseline all over your feet just before you go to bed too. Don't rub it off before you get into bed though. I know it is messy, but it should help with your problem.
SO they can sleep
Usually you do this so you dont pee in the bed. Yet it can be more comfortable than holding it all night. You most likely would pee before you go to bed so that you dont wet the bed. Also it may be more comfortable for you than to hold it all night.
Well first dehydrated what? Second, dehydrated just means lack of water, so if you add/drink plenty of water then you won't become dehydrated.
No, It just means that you have become dehydrated over night and need to drink more water before bed. If you stop have a period then you may be pregant, if this is the case you should see your doctor.
to get all the oils out of your skin so that when you go to bed you dont have oily skin the next morning :)
Yes, if severely so.
Nothing can cure a hangover, exept time. But things can make it better. A hangover is where the alcohol in your body makes your body dehydrated (so you feel awful). So my recommendation is before you go to bed drink as much water as you possibly can. But in the morning avoid fatty foods, drink loads of water or smoothie or sports drinks because the latter two replenish the vitamins.
41 % of people read before bed
You write it like this, "Take before bed."
If their mouth is dry inside, they are dehydrated. If it is a little wet, they are fine. If your baby bird is dehydrated, make sure you dampen its food a bit more so it can more liquids.