There is a cup on my desk. I drink water from it. I haven’t washed it out in ages; it only holds water, is usually drained by the end of the day, and is bone-dry by the morning.

Every so often I fail to finish all my last cup of water, and the remainder stands in the cup overnight. Formerly, this was no problem, as it would almost invariably be refilled, drunk, and left out to dry the following day. This zero-maintenance personal hydration system worked without flaw until Monday, when I developed an inexplicable thirst for Mountain Dew that lasted until this morning.

I left half a cup of water in the cup when I fled the office last Friday, and it sat at my desk, wet, lukewarm, and undisturbed, until lunchtime today, when I raised it to my lips and proceeded to knock back a hearty draught of the good old H₂O.

I barely suppressed the sudden, overwhelming urge to spew the contents of my mouth onto the keyboard. It was the second foulest-tasting thing I’ve had in my mouth within recent memory; it tasted like licking the inside of a fishtank. It was no longer water; despite the absence of any detectable odor or visual cues, there was no mistaking I’d just attempted to ingest a serving of Cup O’ Algae®. Nasty stuff, that. Time to wash out the cup. Just as soon as I finish gargling this soap.