Nicotine dulls hunger. I can assume that nicotine, being an H-cholinomimetic in small doses, increases the production of adrenaline, which in turn increases glycolysis and lipolysis - thereby releasing pit. substances, and thereby letting the body understand that it is no longer necessary to eat. Celery will help just as well. Well, you know this trick - chewing it takes more calories than it gives. I can also recommend fiber. Really sold in stores. Will very, VERY dull your hunger by filling you up.
As for the water, they correctly said, but there is a life hack. If you drink some water with lemon, or even better if it is warm (at least at room temperature), then your appetite disappears for about an hour (I've checked it myself, you may have it differently).
In general, only habit reduces appetite. Eat a lot all the time, can't hold yourself back? Take a 300 ml serving and consume that 300 ml every 3-4 hours, on a schedule. Just take into account that there is food that is digested quickly, and there is one that satisfies hunger well and for a long time), for example, it is necessary to make a bias towards animal and vegetable proteins, complex (this is very important!) Carbohydrates. But of course, you will have to forget about simple carbohydrates. When you get used to small portions, when you feel what hunger is, it will be easier for you to navigate your diet.
Water, and the most ordinary one, without everything. On publics of anorexic women it is often said about "drink some water." to prolong this pseudo effect!