The phrase "big jug" typically refers to a large container, usually made of glass or plastic, that is used to hold and pour liquid, such as water or juice. Full definition
I recently bought 3 big jugs of vodka for making vanilla extract as well as tinctures. (theprairiehomestead.com)
I left the hospital with a wonderful big jug with an attached straw that I filled every time it dipped below one - quarter full. (rookiemoms.com)
We get our drinking water in big jugs because they say we shouldn't drink the lake water; I suspect in an emergency it would be fine, particularly if I had a bit of bleach or purifying tablets. (treehugger.com)