That lemonade was stupidly high, 390mg caffeine. Only serious addicts could drink that without noticing strong effects.
What’s most remarkable about that case, is that it was a Panera. Could have added 50mg and it would still be more caffeinated than I would expect of the establishment. There was no need to go to the extreme end.
Even the strongest energy drink I've ever seen sold retail in the US had "only" 300mg of caffeine. And it came with plenty of signage on the packaging, indicating very prominently how high the caffeine levels were. I usually drink 200mg a day total (sometimes, but rarely, crossing into the 300mg territory), and you were totally correct, there is absolutely no way to not notice when that 300mg comes from a single drink.
In no world would I expect a random caffeinated drink at Panera to go above that.
What’s most remarkable about that case, is that it was a Panera. Could have added 50mg and it would still be more caffeinated than I would expect of the establishment. There was no need to go to the extreme end.