A common trick is to use a spot of superglue so the cap “snaps” as you expect.
For some of my travels, I was told to check the shape of the ice cubs. The little rings with a hole in the middle come from businesses that use filtered water, and were considered safe. Standard cubes or other shapes that can easily come from your freezer were suspect.
Obviously check for local information before assuming this is true wherever you are, though.
I was careful to only buy bottles with new caps in Thailand and then saw a store with a bunch of replacement caps and rings.
Apologies if this is too much of a hijack, and fine if someone reports this and mods want to shut it down - but I think this is directly related:
Water is definitely an issue. And … so are other foods, in particular raw vegetables. Think about what you want your strategy to be, whether for a short or long term visit.
My experience: I have been blessed with a pretty good immune system, apparently. In my years of living in developing countries, I was about a 4 to 6 on a scale of 1 to 10, where 1=totally unconcerned, will crap in a local toilet with no handwashing facilities and then devour raw produce handed to me by a sketchy-looking local; and 10=must wear hazmat suit at all times and am convinced all vegetables want to kill me unless they are completely overcooked.
I had a friend who was a 10. He had a very simple rule: I WILL NEVER, EVER EAT A RAW VEGETABLE IN A DEVELOPING COUNTRY.
I thought that was ridiculous. However, he managed many decades without ever experiencing gastrointestinal problems. I, on the other hand, also did great, but did nearly die just one time. (Long story, don’t need to tell here, summary: got very, very sick, antibiotics, lived).