Plastic containers have a recycling triangle on them with a number inside of it. This will tell you if they are food grade or not. It’s best to stick with slick plastics for water storage. There are not porous. Empty bleach bottles work great.
That’s why I stick to the food container rule. If it’s a bottle food came in, it’s safe to use.
The exception being milk bottles. I have never found a way to get rid of the eventually rancid milk smell.
Someone told me once the milk proteins bind to the plastic and there is no way to clean it totally.
So I just pitch them.
Oh, and BTW, being a home brewmaster who makes beer and cider, I’m well familiar with the processes of disinfecting/sterilizing containers.
Home brewing is a great hobby!
If you have water and you are unsure if it’s safe, you can always add a bunch of sugar and yeast and ferment it!
Bathtub gin!