Humans can survive drinking ryncol, although it is apparently unsafe for volus. One obtainable datapad contains a complaint made by a pirate about how the YMIR Mech he purchased "leaks [fuel] like a volus after a mug of ryncol."
When Commander Shepard visits the Dark Star Lounge and asks the bartender for five consecutive drinks, the Commander will be given a glass of ryncol. The bartender jokes that Shepard will "set off radiological alarms" after they drink it.
Ryncol apparently has "pure" and cocktail variants. The turian bartender in the Dark Star Lounge creates a green ryncol mix served to Shepard by mixing separate components together. As per his prediction, it does indeed knock Shepard out, leading to a short sequence where the Commander groggily wakes up on the floor of the Dark Star's bathroom. In Jack's opinion, Shepard's stash of creme de menthe in the Personal Apartment can sicken people more than a sample of pure ryncol.
Vomit from ryncol consumption is apparently purplish in color.