Not more than 1/16 of a coffee spoon, otherwise it will be dangerous! In a case report in ‘Swiss Medical Forum’, a 36-year-old man described which has taken a caffeine-containing product.
The doctors came to the conclusion that he has suffered a heavy caffeine monointoxication. In the extreme dining area - if the competitions go over days and nights - athletes and caregivers want to distribute the fatigue with caffeine. It is very worth reading the article and see what can happen if you get too much caffeine, see https://www.medicalforum.ch/docs/smf/2015/12/en/smf-02223.pdf