TLM and I have our own ways to get around it though.
If we are getting sushi, we take a reusable box each from home, along with our own chopsticks - I do anyway - TLM is happy to eat with her hands.) This only works if it's one of those shops where you choose your own individual pieces - not so well with St Pierre's where it's all pre-packed and sitting on the counter.
Taking our own boxes has also worked for our local Indian, Vietnamese and Malaysian takeaways (in most cases they are boxes that came with our earlier takeaways from there). It's surprisingly easy to just ask if they'll put the food in our containers, and so far every one I have asked has been fine with it.
Another option of course, is to dine in at the eatery. No boxes and no washing up! Though amazingly I have been to coffee shops where they serve up your coffee in a disposable cup even if you are drinking it on their premises!
Fish and chips - a relatively sustainable option (as long as you don't think about by-catch), in that it's all wrapped up in plain paper which I can later rip up and put in my compost bin.
Which makes McDonalds sound not so bad, regarding packaging anyway. Their straws are plastic but most of the stuff is packed in cardboard,which is recyclable (when it's clean ) and compostable (when it's not). I just hate eating their food.