When you are telling lies; of course your higher centre- brain, knew you are not speaking the truth. Hence, your sympathetic nerves, (which is not under your control) will take over to stimulate thirst centre and start to reabsorb water from your mouth. Hence, you become more thirsty. And, you will consume a sip of water, without knowing the fact. Those who knew, will catch you red handed.- Dr. Rajashree.
Moral of the story, don't lie and drink at the same time.