Another soapless way is to put them in the oven.
Load up the oven then turn it on to 350. Hold it at 350 for like five minutes. Turn off the oven and let them cool overnight.
Perhaps you could put a small amount of water in the bottles and put a bit of tinfoil on the mouths.
Stack them in there laying down.
In How to Brew Palmer suggests that you put foil on bottle place in 350 oven for a minimum of 30 min that will sterilize the bottles and the foil on top will keep them that way until you pull off foil.