Hmm. That's a good point. I wonder if there's trouble lurking there.

The government proposals will make it illegal to sell high-caffeine energy drinks containing more than 150mg of caffeine per litre to anyone under 16 in England.

Aight, so that's their red line.

https://www.healthline.com/nutrition/how-much-caffeine-in-coffee

A 12-ounce (oz) cup of brewed coffee may contain 113 to 247 milligrams (mg)Trusted Source of caffeine, whereas a smaller 8-ounce cup can contain about 95 to 200 mg.

Hmm. A liter is 2.8 times larger than a 12 fluid ounce cup, so that'd be 318 mg/L to 696 mg/L.

goes looking for tea

https://angelinos.com/blogs/news/which-tea-is-the-most-caffeinated

#1 Black tea: Between 64 and 112 mg of caffeine per 8-fl oz serving

4.23 of those in a liter, so between 270 mg/L and 473 mg/L.

It looks like tea and coffee

at least were they energy drinks

would have too much caffine.