My 19 year old daughter Indra was hooked on Coca Cola too! About 1 month ago, she told me she never falls asleep before 4am . Then I realised that the amount of caffeine might be the cause. She promised she would try to stop drinking Coca Cola.
After 3 days, she told me she had slept from 11pm to 9am!!
She is so happy now for my good advize (and I am happy that it worked); she even convinced her friend Matthias to stop too