There is a tiny region in your brain called the hypothalamus that is believed to have some say on when you feel hungry and thirsty, and it doesn't speak with words so its messaging can be misunderstood. When you are just a bit dehydrated, you can easily misinterpret that thirst as a need for food.
Because advertising can trick your craving for refined sugar and fats to hijacks those thirst signals, most of the times when you suddenly want to buy a soda, grab some Namawojolo, or order a Kikalayi, you're likely just ignorant that you're thirsty.
It is better to start with around 300ml of water when you feel hungry outside of your normal meal times, or when you believe to be craving something sweet or fatty. Give it about 10 to 15 minutes. Most of the time, the craving will just fade away because your body finally got the water it was actually asking for.
Unless you're pregnant or sick, of course—in that case, just listen to your body(and doctor maybe) and eat.