We have used milk jugs to store water for years.
As soon as they are empty of milk we wash thoroughly, rinse them well and leave with caps off to air out.
When dry we give them the smell test before filling with water.
Any with an odor get recycled but there are very few that fall into this category.
I suspect that leaving empties around awile before washing them makes them more likely to go off but I have never kept track.
I do know it makes them harder to clean.
Every storm season we fill any empty ones with tap water that is chlorinated at the water treatment plant.
We used to put a little bleach in each jug but stopped a few years back and have not had any problems.
I figure there is enough bleach in the city water to make more unnecessary.
However, If I was going to store water for several years I would go back to adding more bleach.
After storm season we gradually use the water in them, air them out and refill.
We have almost never had a problem with water being off, even after stored for a year.
We also use 2 liter soda bottles and other containers but I like the milk jugs for their ease of handling and storing.
I believe you can get the smell out using baking soda. A quarter cup of soda to a full gallon. Let sit for a day or two then rinse. Should have a fresh smell. If not repeat. But I still wouldn’t use one. Somehow the milk gets into the pores of the jug and you can’t get it out. You can get those blue cast jugs at WalMart where the water machine is. I think the gallon jugs are a buck and a quarter. They have several sizes.
I freeze water in 2 liter bottles. Helps keep the freezer filled up and save energy as well as having a back-up of water available.