I keep one keg dedicated to root beer. Kellie has special requests for root beer, and I made up a batch tonight.
My favorite mix is Sprecher root beer out of Wisconsin. Actually, when I go to Iron Mountain to visit my parents I can find it in the stores. This stuff is pretty good and really easy to make. It comes in a one gallon pre-mix jug, and you just add it to a keg with four gallons of water. The only downside is it's pretty expensive and I need to ship it in.
This time, I'm trying the Gnome brand mix. It's cheaper, but it's only four ounces. The standard recipe is to use 2-4 ounces per 5 gallon batch, and add 10 cups sugar. I made this once before and it didn't blow me away, so I thought I'd change it up a little. I used the entire pack for the full 4 ounces. I then made it with 5 cups of brown sugar, four cups of cane sugar, and 3/4 cup honey. Looking it up, I thought that should get me about the same sweetness as required 10 cups of sugar.
I heated the whole thing up to 160 or so and then dumped it into a sanitized keg. The thought was just to try and sanitize the whole works. My only screw up is I forgot to filter the water. Hopefully that won't make too much of a difference.
http://daytonroadbrewing.blogspot.com/
I've made some soda with yeast and was never really happy with it. It was inconsistent and, of course, there were floaties. For some reason, non-brewers don't appreciate floaties... Another idea is you could just make up a 2-liter batch, and use a Carbonator cap it the bottle. Just chill, and shake until you get it carbonated.
I posted about homemade carbonator caps in the Gadget section.