Goo-Gone is the best commercial product that I know of. It readily dissolves just about anything sticky or greasy. I've also used common naptha lighter fluid. Not only does it remove the stickers, but it also gets rid of the sticky residue and polishes up your jug a little bit. Another option is to just use plain hot tap water. My tap water usually runs around 110°F, so it won't melt the plastic. Run hot water over the surface, peel off the stickers, then scrub the residue off with a plastic scouring pad (don't use metal, it'll scratch). It's not the quickest method, but it will do the job, plus it's extremely cheap.