Since caffeine is a mild natural diuretic it can reduce the amount of saliva produces. Usually since it’s only a mild diuretic this won’t happen to you unless you don’t drink water throughout the day. Energy drinks also enhance the amount of electrolytes that’s in it and too many electrolytes can cause you to feel ill. Drink lots of water, slowly, and you should start to feel better. If you continue to feel Ill then go see a doctor. I myself am not a doctor nor am I qualified to give such an evaluation therefore this answer was formed through research and knowledge I’ve formed over the years so take this with a slight grain of salt.