No sugar-coating here (pun intended:)
It's easy to say that soda is not good for people. But I think once you find out WHY it is bad and how much more it is damaging to developing system of children, maybe even your husband will give up his habit.

http://www.rodalenews.com/facts-about-soda

And diet versions aren't any better.

http://healthyliving.msn.com/health-wellness/7-side-effects-of-drinking-diet-soda

Good luck breaking the habit! Fingers crossed!