Sweat Rice is a Trinidadian old wives tale about women, who right after boiling a fresh pot of rice, allow the steam of the rice to flow up into their vaginas. The resultant liquid or "sweat" is left to drip back into the pot of rice. The intention is to trap the man in a relationship or as a spell to make him fall in love with her. This superstition is strongly linked to "Obeah" spells some women may employ to ensure their lovers devotion and loyalty and bind them spiritual to a relationship. Hence the saying that one must be careful where one eats. It is also connected to the belief that spiritual energy of whoever cooks, ultimately affects the food. Some people will not buy or eat food from certain places if they sense a negative energy from those who prepare their food.
This youtube video tells a story of a woman who "sweats" some rice to attempt to bind a man to her: