We have a capper, a funnel, and lots of unused crown caps. Our capper came from an antique shop, but they are always on ebay as well and not expensive at all. You can buy blank caps made for home brewing, or buy them in bulk with old logos on them. Our current batch are Hires Root Beer. We go buy the 3 liter bottles of Coke/Dr. Pepper to fill the bottles with, since that is the cheapest route. We fill the bottles to within about 1 1/2 inches from the top using the funnel, then cap them with the capper and wipe them down so they aren't sticky. As long as you get a good seal (read: push down pretty hard with the capper), they will last a good long time. We still have 2 or 3 bottles of Dr. Pepper that was bottled about 5 years ago and were what was left in the S-48 when the freon line split inside the machine and leaked out (still need to get that fixed, got a quote for $300 from a guy here last month
). I opened one, and it still was as fizzy as when bottled. Again, the better the seal, the longer it lasts. Make sure your old bottles don't have any flea bites in the rim. I've only ever had one of the DP bottles break while vending down the chute in the S-48, and it may have had a stress flaw somewhere.
It usually took us about 30 minutes to fill and cap enough for a full load plus pre-cool in the S-48. It's fun, like you said, and well worth the effort!
