If you are working with kiln dried wood then glue really isn't necessary when everything is fitted tightly together because when you soak the bucket in water it should swell up like a tick. At least that is what the coopers do when they build barrels and buckets.
Look online for "Brewer's Pitch" if you are concerned about any bad flavors coming from the wood, Brewer's pitch seals the wood nice and tight, but I don't know what it is made of. It ins't supposed to react with water or alcohol