Arabesque stated 12 oz of Diet Mountain Dew is 300mg.
"It doesn’t have sugar but it does have artificial sweeteners which continue to feed your sugar cravings. Plus the 300mg of caffeine per can is equivalent to about three 8oz cups of coffee"
That is categorically false.
A 12 oz can of Diet Mountain Dew is 54mg or 55mg depending who you ask.
Information Sources:
Harvard:
A 12-ounce can of regular or diet dark cola contains about 40 mg caffeine. The same amount of Mountain Dew contains 55 mg caffeine.
https://www.hsph.harvard.edu/nutritionsource/caffeine/
Examine.com:
(an independent and unbiased encyclopedia on supplementation and nutrition.)
55mg
https://examine.com/nutrition/caffeine-consumption/
University of Utah
55mg
https://www.math.utah.edu/~yplee/fun/caffeine.html
Caffeine Informer
54mg
https://www.caffeineinformer.com/caffeine-content/diet-mountain-dew
