You will need:
The dew collectors drop from Thistleshrub Dew Collectors in Thistleshrub Valley, south west of Gadgetzan. Pick up the  quest while you're in Gadgetzan as the mobs for that quest are in the same enclosed area as the Dew Collectors.
I've got an idea, see. I've heard of some strange creatures called dew collectors that live to the southwest... and that they are able to store water in special glands.
I think that if I could get one of these glands, I could create a drink that would quench my terrible thirst! Do you think you could help me, <Name>?
Look for the cactus garden, <Name>; that's where you'll find the dew collectors.
Please, tell me you found the dew collectors?
Oh, wonderful! Give it here -- let me drink it!