You can start this quest after visiting Kadara for the first time during the quest "Hunting the Archon". Return to the Nexus and head to Kesh’s office on the Operations deck, outside of which you’ll find a woman named Wilma, who has a request to make of you. Seems like she wants to surprise Kesh, who is dissatisfied with the stock of hooch on the Nexus, and would prefer something with a bit more bite. The unregulated and quite possibly dangerous bathtub booze on Kadara might just tickle a Krogan’s tummy. Don’t worry, Krogan have redundant organs. It’s probably safe.
Fly back to Kadara Port and head over to the Arms Merchant. She doesn’t happen to sell any alcohol - nor should you drink anything that qualifies as a weapon - but you can read the Datapad "Best Booze in the Universe Has Moved!" on the counter of the stall to find out that you’ll need to get your boots dirty if you want to acquire a beverage fit for a Krogan. You’ll get 530 XP for this bit of light reading.
Take the lift down to the Kadara Slums and enter the badlands, and from there fast travel to the Sulfur Springs Forward Station. From there drive the Nomad up the road to the northwest, then at a fork turn northeast to reach the Kadara settlement site. Dismount the Nomad here and make your way southeast to a toxic lake, which is where Zed’s navpoint directs you to. Circle around to the southern side of the lake (assuming you haven’t activated Kadara’s vault, in which case, just wade through the water) and make your way to a shuttle on a small island. Talk to the Bootlegger to get your booze and earn yourself 530 XP, which technically completes the quest, although you can return to the Nexus to get an update from Wilma, if you care.