Imagine your standard, medium-sized plastic water bottle you grab from the store. That bottle is usually about 16.9 ounces. To hit 91 ounces, you’d need to drink about five and a half of those little guys.
Another way to look at it: that big glass pitcher you use for lemonade on a hot summer day? The one that holds about half a gallon? 91 ounces is just a little more than that pitcher full to the brim. So, it’s not a swimming pool, but it’s also not a single sip.
It’s basically the size of a classic Nalgene bottle (which is 32 oz) times three—minus a few gulps. It’s a healthy, human-sized amount of water for an average adult to aim for daily.