I use an ordinary glue stick - the labels wash right off in warm water.
Of course, if you drop the bottles in a cooler and they get wet, the labels tend to come off prematurely - so I always put a little round sticky label on the cap so nothing ends up unidentifiable.
Both the glue stick and the 3/4" round labels are available at any office supply.
"We are here to drink beer. We are here to kill war. We are here to laugh at the odds and live our lives so well that Death will tremble to take us."
-- Charles Bukowski