My puppy wakes up at 4 AM, how can I get him to sleep longer?

Some pups wake up in the night/early in the morning to use the bathroom. It's often a factor of physical maturity and the ability to hold their bladder all night. I have had 8 week old puppies that sleep for 8 hours or more from day one and others that still are getting up in the night at 7 months old. They're all different. There is no trick to getting them to sleep longer, it's just one of those variables in raising a puppy. Try removing water access earlier and see if that makes a difference.