He was so tempted to say something ironic about not needing meals when coffee was at hand, but Al was entirely too likely to take him at his word, and Severus had spent too much effort already in weaning Al from a serious caffeine-and-sugar addiction.
So instead he merely inclined his head and murmured "Touche." in response to Al's comment about meals.
And then Al went on to ask that question. It would've been far too easy for Severus to lie. But he'd made himself a promise; he was determined to never lie to Al unless it was absolutely essential.
And this didn't qualify. So he sighed, and murmured, "Saturday lunchtime I was thinking over what should be done as a result of my researches the previous lunchtime. ...Friday lunchtime, I interviewed the Widow Lestrange." The title was spoken with a twist of Snape's pitch-black humour.