If you are the type of lazybones who, rather than washing their coffee cup after each use, simply pours fresh coffee over the evaporated residue of yesterday's cup, I have good news for you. You don't actually need to wash your coffee cup every day.
Photo by Kate McCarthy.
According to the Wall Street Journal, washing your mug at work is actually the much less sanitary option, given the fact that everyone in the office is using the same soggy sponge to scrub up. As infectious-disease expert Jeffrey Starke told Heidi Mitchell of the WSJ, your coffee cup does have germs in and around it, but they're not germs you really need to worry about:
"If I went and cultured the average unwashed coffee cup, of course I'm going to find germs," Starke said. "But remember the vast majority came from the person who used the cup."
Of course, this only applies if you're the sole sipper from said vessel; sharing with another person defeats the whole "one mug, one set of germs" situation. Another caveat: You're going to want to wash if you use cream and sugar, as those can cause mould growth. You should probably wash it at home, though. That communal sponge is bad news.