How to get husband to drink more liquids..?

First of all, how dark are you talking? If it is brown or even darker than that, that is a sign that waste (not urine, but small bowel movements) are being let out instead of urine, and that is an emergency. However, if it's just dark yellow then it's okay. To get him to drink more, I'd give him something that he may actually enjoy - gatorade, vitamin water, etc. Something that tastes somewhat good.