Dialect tests. Think about how someone from boston might say "park" like "pahk" vs other parts of the country, or if someone uses "y'all" where they might be from. The way people pronounce o,a, ai, ough, augh type of sounds is very telling. Also phrases are very regional. There are many studies that compile that data. One famous dataset is used in a Times article that is behind a paywall, here are some people talking about it: https://peabodyawards.com/nytimesdialectquiz/
Another random one from buzzfeed: https://www.buzzfeed.com/andrewziegler/dialect-quiz
And babbel: https://www.babbel.com/en/magazine/american-accent-quiz
Or just search for dialect quiz.
And then I "remembered" to buy more but forgot to bring it into the bathroom and think I need to get more, and forgot I bought some, so I "remember" 2 more times when I'm getting groceries, and now have 3 bottles sitting on my kitchen counter now.
I just went to put one in the shower and left the other 2 on the bathroom counter. So I'm good for a while.