You get free water with the coffee, use that water to get a free tapa, and use that tapa to exchange with your neighbour for their water.

Pretty soon you will have secured all the water in the restaurant, which you can then use to barter for a coffee, which will give you free water (if they have it), thus tightening the grip on your market supremacy.

Then you broaden your horizons and set your sights on the red planet. If anyone calls you a fool, confiscate their water and drink more caffeine, and if anyone tries to take your caffeine away, send them away to the red planet