To start this quest first you need to make another short quest called "It Smells Delicious" from the Guard Stan in Town of Oren
For the quest "It Smells Delicious" you need to go in Sel Mahum and hunt Sel Mahum Squad Leaders until you get 10 Sel Mahum Diary and Sel Mahum Chef until you get 5 Sel Mahum Cookbook Page.After this you go to Guard Stan again to receive your reward (xp/sp and some adena ) and then you are able to take quest "No More Soup For You".
Start the quest talking with Guard Stan in Town of Oren .
He will tell you to go hunt Sel Mahum Escorts,Sel Mahum Chef,Sel Mahum Squad Leaders to gather "Full Barrel Of Soup" and "Empty Soup Barrel.
When you start the quest you will get also 500 Foul Fruit that you can use to get faster Full Barrel of Soup
To use Foul Fruit you need to wait until Sel Mahum Chef bring the soup to the Squad Leaders,they will stay near the fire and eat and in that time you put Foul Fruit in their barrel with soup .Smoke will be over the Sel Mahums and they will attack but beacause of the Foul Fruit they will have less HP than usual.
To get reward you go back to Guard Stan with Empty Soup Barrel and Full Barrel of Soup
For 2 Empty Soup Barrel he will give you 1 Full Barrel of Soup and after that the reward depends on how many Full Barrel Of Soup you bring
Keep in mind that Reward is random!!!