The only way we got coke smell out of plastic barrels was to lay them in the sun for a week. Take the caps off, lay the barrels with one opening up. Reason being, the hot air rising will exit the top hole, pulling fresh air into the bottom hole. We flipped the barrel openings once a day. It took approx 5 days for 30 gallon barrels. The white barrels deodorized faster than the blue barrels. We tried the Clorox, but it didn't work well. The fella at the coke distributor recommended the "solar" way.
FWIW