Dehydration

What do you do when baby is dehydrated? I've been offering nursing much more often to ensure he's getting liquids, but he's having diarrhea every time he nurses. I read online no pedialite until after 1. My 9 month old hasn't went a diaper in almost 5 hours, but he's nursed twice both sides during that time and had breakfast. Any suggestions??

**UPDATE: I've been trying water in a bottle and all he will do is chew on the nipple. He won't drink any of it.

He also just finally wet his diaper a little at 9:49am