FULL DISCLOSURE: This is stolen from poster Mark Whiz on Modern Muzzleloader, but I'm not feeling real guilty because it's too good to not pass along.
In response to a post asking for guidance on cleaning .25ACP brass, Mark Whiz posted the following.
A quick way of cleaning brass (since you don't have the usual handloader equipment like a tumbler) is to soak it in a bowl of Cider Vinegar for 20 to 30 minutes, swishing occassionally, swab out the inside with a Q-tip and rinse well in clean water, then dry. I clean my pistol brass this way from time to time to clean out the case insides and primer pockets. Keeps 'em pretty shiney as well.
Well, I tried it myself with plain white vinegar and it worked great - even better than my vibratory case cleaner. So well, in fact, that I'm going to add a four ounce plastic bottle filled with vinegar to my shooting box so I can drop the freshly fired cases in it right at the shooting bench.