The largest Big Gulp is 50oz and when I was a kid, people leaned on free refills for them. A 50oz is almost a whole 2-liter.

You're not wrong, it's not the best example, but I've seen people go through numerous Big Gulps a day.

Hell, when I worked overnight as a security guard, one of my fellow guards who drink an entire 2-liter of Mountain Dew to himself every night.

It's hard for me to think about because I can't even get through a whole 16oz without stopping halfway because it's too syrupy.

Very arguably, with 1970's manufacturing standards, and how much 32 ounces of liquid weighs, it was an engineering feat at the time. So much so that the originals looked more like a milk carton.

https://physicalculturestudy.com/2017/08/31/the-history-of-the-big-gulp/

Potts’s desperation caught the attention of Coca-Cola, who in 1976 sent representatives to the merchandise manager with a strange proposition. Coca Cola wanted to create a new 32 ounce cup for their drinks, a previously unheard of amount. The largest size at the time was 20 ounces, and even that was considered to be monstrous. Instinctively Potts refused, claiming that the Cups were “too damn big” and in Potts’s defence, he was right. The design for the 32-ounce cups was square on the bottom and resembled your average milk cartoon.

Not a feat of engineering, a feat of marketing

Agree. Even recently, I would have up to 5-6 cans worth myself (have since cut down a lot), but alongside the financial cost, there's also the acid eating away at your stomach lining and the excess caffeine to worry about alongside the Aspartame.

Frankly, given the stomach issues and acid reflux that too much soda can give you, I would imagine that people (even sodaholics) would have to stop much sooner than 20 due to all the other issues involved with sodas before the problems with Aspartame would even come into the picture.

Not to say that I'm not leery of Aspartame, but diet Soda has other major issues beside it.

You're not wrong, it is nuts, health-wise and financially!