Several sites I found list Guaraná Antarctica as having 30 mg of caffeine vs Coke's 34 mg [0]. It is also similar in sugar content contrary to what I initially found.
That doesn't match with my personal experience comparing the effects of Guaraná Antarctica and other sodas (eg Coke). Also, websites in Portuguese [1] claim that Guaraná contains only 2-4 mg of caffeine per 350ml. I wasn't able to find an official source.