Lots of locals in Hainan chew betel nut, a red seed that turns your teeth red. The effect of chewing betel is compared to nicotine or caffeine, or maybe chugging a Red Bull.
The cultivation of betel nuts is interesting—it grows on a creeper vine around a tall pole, in carefully maintained rows. The nut is usually wrapped with spices like cardamom, saffron, cloves, aniseed, turmeric, mustard, or some kind of sweeteners. Alone it tastes like pepper and warms the inside of your mouth.