Possible Clues:

• Indigestion
• Heartburn
• Remedy sipped, say, for indigestion
• 'It was enough to make any man sick,' as Pepys said, wrongly
• A spy spied - hence that uncomfortable feeling?
• Sipped, say, stew causing stomach upset
• Foolishly sipped, say, it produces indigestion
• Article out of Times energises one with a digestive problem
• A spy spied trouble with illness
• Pepys said to suffer from this?