I got my first 275 this year. It contained a liquid yeast and the residual had a very stron ammonia smell. I flushed it out with water til it ran clear out the drain, then filled it with a bleach/water mixture and drove around for a few miles.

I drained it, and the ammonia smell was gone, but the bleach smell was there. Filled and drained two more times, and its clean as a whistle with no odor.

Last year, I got two 55 gallon drums that contained chicken broth. I rinsed, and scrubbed with dawn and hot water. Rinsed again, and then bleached, follwed by two more rinses. I could still catch a wiff of the broth, but it was faint. I was nervous, but the syrup that came from those barrels was just fine.