I picked one of these up in Nakhon Phanom, its a mini fast home brew pot. You fill it with sweet liquid, traditionally coconut or palm juice, and leave it in the warm to ferment for 15 minutes or longer. Dried yeast inside ferments the juice into a semi-alcoholic drink.
Although juice or sugar sap is traditional, one of the best flavors to use is Sprite! It's sweet enough to give the yeast something to work with, and the herbs in the pot work well with the lemon/lime flavors.
I used young coconut juice for mine, young (green) coconut is a little sweeter.
When you buy the pot it has a cement top, break this with a hammer, the herbs are protected by a piece of plastic, you simply remove this. Fill the pot up with Sprite or Coconut juice or your chosen sweet drink. Leave it at room temperature for 15 to 30 minutes, then drink it using the provided slotted bamboo straw. The straw prevents the herbs being sucked up.
The pot is re-usable several times till the flavor is all used up. It's very similar in principle to Ya Dong, the herb infused spirit sold on the streets of Thailand. But with a little home brewing thrown in for good measure.