I had just such a chance this past weekend at a church picnic party and thought I'd document the fun so you too can make garbage can root beer some day!
First of all, I always forget the amounts of stuff, and I'm not totally sure that the recipe on the back of the root beer extract is what we've always done, but I found this ingredient list at All Recipes, which is what I ended up using. If you don't want to make a HUGE batch of this stuff and just want a "normal" bit, then make it in a 5 gallon jug instead of a garbage can!
Here's a list of the both ways:
For a Five Gallon Jug
6 cups of sugar
3 1/3 gallons cold water
1 2-oz bottle of root beer extract
4 lbs dry ice
For a 20 Gallon Garbage Can
(times the above by FIVE!)
30 cups of sugar (15 lbs of sugar!)
16 2/3 gallons of cold water (give or take a bit!)
5 2-oz bottles of root beer extract
20 lbs of dry ice
So here's what you do.
First, buy a new plastic 20 gallon garbage can! And if you plan to make this often, you of course keep it handy and store it garbage free.
Fill the can up with water about half way and then add the sugar and extract. Stir with some sort of long implement (we tried using a hot dog roasting stick this last time, but I wouldn't recommend stirring with a fork. Doesn't work too well!)
Or, if you aren't bugged by it, stick your arm in and stir the sugar so it doesn't settle too much at the bottom!
Fill the can with the rest of the water, which you'll want not all the way to the top, thus, about 17 gallons as listed above.
Then, the fun part! Carefully and safely drop in the dry ice. Let it bubble and fizz for about an hour. It's during this step that I hope the sugar truly gets stirred up, because it's pretty impossible otherwise! (Be sure to not put the lid on, that would be explosive!)
After an hour, taste it to test the fizz level. If it passes, you are done! If not, let it percolate a bit more. To serve it, we transfer the root beer with a gallon pitcher to the 5 gallon cooler, so people can easily fill their glasses.
And then, bottoms up!
This amount served well over 100 very thirsty people the other night, and we had a good couple of gallons left over.
Seriously, this is one of the best summer treats ever!
Oh, and if you are at a big gathering, I would keep your eye on on the can during the actual picnic, or at least put a note on it declaring it NOT garbage, or you just might end up with a picnic plate thrown right in!
Also, if you happen to have some vanilla ice cream handy, well, you know what that means! Floats!