Just Bento

My bentos get washed at home, but my teacups get washed in the public restroom.

I keep a bottle of detergent and a clean dishtowel in my desk. I go to the restroom with cup in hand and towel over my shoulder. I make sure that the cup doesn't touch ANYTHING but water while I'm washing it. After it's dried, it goes straight back to my desk without touching the counter and the towel gets frequently washed at home.

You might find it useful to get a small basin for doing dishes in the office, if it's convenient for you to wash bento at work. You'd have a clean surface for letting your bento dry, you could keep it in your own workspace, and you could store your own sponge/detergent in there as well. I kept such a basin with a dishrack in it when I had nasty roommates who left filthy dishes all over the kitchen.

I use the kitchen facilities at work much the same way, as a place to rinse my bento. I accept that the kitchen and all washing utensils at work are filthy (they wipe down the counter with the dish washing sponge, which is never sterilized to my knowledge) so my main concern is getting the main part of whatever my lunch was out so it does not by chance end up in my bag and make it easier to clean the container when I do get home.

I'd love to do that but... i work in consultancy, which means most of the staff at the office do not have their own desk with the name label on it. We are provided laptops and a little lock (wich is wide enough for the laptop but for nothing else!!) in which we receive drafts or our cellphone bills and so on. We have free-to-use desks that we can use for one day, and change for the next day, and so on. (this makes me think the desks are more important than us, the staff ¬¬)
This is because we do not have to work at the office every day (we usually spend several weeks or months at our client's office).
So i can't keep my own sponge and detergent because i have no place for it!!
I can't even have my own mug ._. (but it's ok, since i can go outside for my coffee, teehee! ^^)

We are lots of people so we cannot buy gear for the sink room or for the lunch zone... So my only solution is to rinse the box and wash it at home! ^^

I could quite easily wash mine at work, but mostly I just take it home dirty. If it wasn't going to spill on the way to work, it's not going to spill on the way home!
We have a kitchen at work with a dish brush that would be absolutely no use to wipe benches with, so you know it's only been used for dishes, but we also have a dishwasher, a boiling water dispenser, and a cleaner who comes in and cleans about three times a day.

I bring the dirty bento box home to wash. Never trust the shared sponge at work. It would be okay to pre-wash with it, and wash again at home, if you only have 1 container to use. I have several bento boxes, so I can soak the dirty one overnight. We have a dishwasher at work but it's really for office items like mugs and some plates and utensils.

Our work kitchen is quite clean, I usually wash my box at work, or at least rinse it.

I try to wash my bento immediately after my lunch break. We have a full sink with dish rack and dish soap always available. I think the boxes will last a lot longer and not stain as rapidly if you can give them a good wash.

Jiza you could pack travel wash set: a tiny bottle of dish soap and a portion of a sponge that you cut in say 4 pieces with you in a purse or work bag. Put them in a baggie or plastic soap container so leaks are kept to a minimum and the sponge doesn't wet other things down. Be sure to set the sponge out to dry at night.

Just a thought.

I bring mine home and wash it. There is a sink in the departmental common room but I don't know if I'm allowed to use it because I've only seen staff use it (same goes for the microwave, and the kettle).