I don't know what "thirst" feels like at all! It's weird because I do feel hunger. If I forget to actually eat, my stomach kicks my brain and refuses to let me concentrate until I fix it. Hydration has no equivalent, and in retrospect, it's no wonder I was suffering headaches and nausea all through college on my diet of mostly soda. After I switched to water as my primary beverage things improved dramatically, but it's not perfect. I still have to watch the signs and pay attention, or I'll dehydrate myself by simply forgetting to drink.