After I consume my beverage, tea usually, I'll take a napkin that I've carried with me and wipe out the container, so that it will not drip into my backpack. I make sure to take good care of my napkin, so it can be used several times. I place the napkin in the cup, with the lid on, and it stores nicely in my backpack while I continue my commute. Once I get into my office, Taking some water and a mild soap, I wash the interior of the cup, then rinse with clean water. I then put the cup upside down on a drying rack (or the napkin mentioned above.)  for at least 10 minutes, after which I'm free to bring the cup back to the original location and get yet another beverage of my choice. Many places will even charge me less money the next time I use the cup, for the exact same type and amount of the beverage. 
I've successfully done this 14 times with paper cups and I do not see an end to using my fancy new plastic cup, just acquired in a 20 oz form. I think this cup may last forever, just not in a landfill. There's not a lot of marketing behind my idea. Nothing to copyright or patent, you're free to share as you see fit. 
I think this idea may even work in different languages and cultures. 
If there' s interest, I'm happy to post images.