A.,
Your son can be trained to sleep alone just like a baby is trained to sleep alone, except a baby is easier because he is confined to a crib.
What I would suggest is that you choose a weekend or preferably a long weekend, in advance, for training him to sleep in his own bed. If you don't already have a bedtime routine including a bedtime story, begin one right away.
Have his room clean and pleasant. Keep the curtains and closet door closed if having them open at night bothers him. To get him used to being in his room in the dark or with a night light, stay with him for a while each night, talking about the day or things around his room.
About a week before the event, tell him that beginning on friday, he will start sleeping in his own bed. You can get him a night light, special pj's pillow, blanket flashlight or sleepng toy to make it seem like a special event. These items are for use with his bed only. You may like to establish a special reward if he sleeps in his bed with out a fight.
On friday night, follow through with the bedtime routine, reading to him in his bed. turn off the light (put on night light if necessary) and talk softly to him for a while, (remind him of the special reward) say good night with kisses and close the door. It might help for Dad to be there, too.
Now expect and prepare for a battle. he will most definitely have a fit about not being able to sleep with you anymore, but you MUST stick to your guns, be loving and insist that he is OK. Don't let him make you feel guilty or think that it is easier to give in. Don't allow yourself to become emotional about it. It will be easier for both if you don't. Be calm and patient. Whatever you do, don't get upset with him--he's going through a big change.
Resist the urge to lay in his bed with him - that will start another bad habit that's hard to break.
Now, eventually he will get tired and fall asleep, but in the meantime you will probably constantly be going to him, putting him back in his room, restating that he is sleeping in his own bed. If he stays in his bed and just screams, that's much easier. Just go console him periodically, first every 10 min, then 20, 30, etc. until he falls asleep. He may wake in the middle of night and either cry or come to your bed. You will then have to go through it all over again. Perhaps your husband can take turns with you. The more tired you are, the less patience you will have.
This should last for at least 3 days, up to a week or so until he realizes that your bed is no longer an option.
Please remember that it will be terrible to go through this, but once he's sleeping in his own bed, You and your husband will be much happier, and your son will be just fine, and will probably also sleep better.
To wean him from the drinking issue, give him lots of water and milk (doesn't NEED juice)during the day so he's not so thirsty at night. Daycares don't give lots of fluids, so you have to do it in the morning and evening - don't ask if he wants it, just give a cup often and tell him to drink at least a little each time. On a weekend night, different from the sleep training weekend (before or after), instead of juice or milk at night, switch him to water only. He will no doubt protest, but if you kindly insist it's water or nothing, he will eventually settle for the water. If he throws the cup in protest, take the cup away and don't let him have it back that night. try again the next night. Be Firm and kind. Let him have one cup, when that is gone, that's it. If you are getting the drink for him at night, tell him if he wants it, he must get it for himself. You may need to make these changes one at a time as doing it all at once may be too much for some kids to handle. Soon, you'll need to wean him from the water at night altogether until he is potty trained enough to go to the bathroom during the night. (buy a plastic cover for the mattress! and have a back up set of sheets and blankets each night)
As the parent, you are in charge, not him. Too many parents feel guilty about telling their kids "no", especially if they are in daycare all day. They allow the kids to call the shots. This is not healthy for the kids or the parents.
My 5yo son has slept with us occasionally and it was amazing that he'd insist on continuing after just one night. Now he prefers to sleep alone.
Good luck!
K.