I am coughing. I need vitamins!

Cola likes the berry flavoured vitamins so much that he demands them everyday, in the same manner as begging for candy.

Cola (fakes a weak cough): "Cola is coughing ah. Cola needs to eat vitamin." 

Me: "But you already have a vitamin today." 

Cola: "Cola is coughing ah. Cola is coughing ah." Repeat ad nauseam x100

Me: "But you already have a vitamin today ah."  Repeat ad nauseam x100

Hmm... let's try another approach.

Me: "Cola, have you eaten your vitamin this morning?"   -Yes

Me: "Well then, how many vitamin should be eaten in 1 day?"  -One

Me: "So what happens if you eat more than 1 vitamin?"  

Cola answers without blinking, "I will die."