Generally speaking when someone reacts to any fast like you did it means that their system is pretty toxic. You also have to consider the kind of diet you eat and what you had been eating the day or week before you began the fast.
Fasting should not be taken lightly and with any cavalier attitude of jumping into a 40 day fast right out of the gate. More so if your system is very toxic and you had been accustumed to the Standard American Diet(SAD) and the biggie if you were a regular coffee drinker or diet sodas that contained caffeine. Experienced fasters and particularly when embarking on long fasts of more than a couple of weeks start by eating a mostly raw food and juices for at least 2 weeks or more prior to fasting to start the system "gradually" detoxing to avoid the Herxheimer* and other violent and/or uncomfortable detox reactions like you had.
You should be drinking water in addition to the lemonades and the maximun or close to the max of lemonades daily to help the system flush out the toxins. The MC is NOT a weightloss "diet". Do not make the mistake of most desperate dieters and cut back on the lemonades to the minimum. The MC or any form of fasting does not work by the restricition of calories.
* the realease of toxins at a higher rate than the system can handle generally causing nausea and vomiting.