From The Stargate Omnipedia
Ceremonial cake of the Chosen on the planet Argos. When a cake is presented it signifies the bearer's wish to marry. Receiving and eating the cake indicates acceptance of the proposal.
The contents of the cake were sufficient to drug Colonel Jack O'Neill, who was unaware of the food's cultural significance when it was presented to him by an Argosian woman, Kynthia. By eating the cake he was also inadvertently exposed to with microscopic nanites created by the Goa'uld Pelops.
Brief Candle - O'Neill eats Kynthia's marriage cake and becomes infected with Argosian nanite technology.