Possible Clues:

• MLK eats in -- cafe guy doesn't have one clean glass?
• Clean liquid below a terrace is doing this!
• Going on the beer for liquid refreshment? Go to The Tap for that!
• Basic need
• Most of the beer from The Palace is great for hydration as it comes from The Tap
• Having pints is subject to taxation? And, that's supposed to be good for you!
• Outpour of many fountains
• English author swallowing mixture of gin and tasteless liquid
• Aqua potabile