Why is my puppy leaking clear fluid in sleep? Is it a wet dream?

This can be completely normal. Nipsey may be getting up trying to get comfortable, and some smegma has come out as he's moving around. It doesn't sound like this is anything to worry about, and you don't need to do anything about it. I hope this helps.

I would recommend that you have him checked out by the vet. The vet should do a thorough exam of the prepuce, a prostate exam, and collect a urine sample to help determine where the fluid could be coming from and what is causing it to be dark. Blood, infection, some immune disorders or dehydration can cause urine to be very dark.

Ejaculate containing sperm should look opaque white, so I don't think it sounds like sperm. It could be very dilute urine that appeared clear, or it may be saliva if he was licking his penis and prepuce. If he is urinating normally and seems to be acting like his usual self I would not be concerned. You should monitor for any wet areas on his bedding or other discharge from his penis and contact your veterinarian if you see these signs.

Unneutered male dogs will masturbate and have discharge from the penis on occasion. This is normal as long as his penis does not stay exposed from it's sheath for longer than an hour or so. If it stays out too long it is an emergency and he needs to see a vet. If you do not like this behavior you can have him neutered which will probably help.

A picture of the amount you saw would help here so we can quantify the amount. However only small amounts should be coming out (not puddles of fluid) and usually it is yellowish/green in color if it is smegma (hormonal fluid from male dogs). If it was colorless and odorless it may have been really dilute urine. Nevertheless it isn’t something to be too terribly concerned about, unless it is a large puddle and constantly leaks. If this was a one time incident I also wouldn’t worry. I hope that this was something incidental and doesn’t continue to be a problem for Sam. If it does then a vet visit is needed to collect samples of this mysterious fluid so that I can be analyzed and confirmed what exactly it is. Best wishes with him moving forward. Take care!

The cause of this discharge is unknown but it is suspected to be hormone related is puppies that have not been spayed/neutered. It has nothing to do with dehydration and it does not make them feel bad/sick. If it really bothers you, you can wipe the discharge away with a baby wipe when you see it. ( https://www.petco.com/shop/en/petcostore/product/well-and-good-hypoallergenic-deodorizing-dog-wipes )

I believe this might be a repeat of a previous question I just answered, so I will post the same answer below :-) It sounds like your dog is masturbating. Unneutered dogs can masturbate and ejaculate. This is a normal behavior, and if you don't want this to continue, I recommend having him neutered as soon as possible. He may continue masturbating, especially if he's learned it feels good, but it will stop him from ejaculating.