I used to make my herbal tea at home, then put it in an insulated thermos to bring in.
I had this issue when I realized I wasn't digesting any of the cold foods I brought for work, so I tried a few things to bring in a hot lunch I wouldn't have to microwave. The one that didn't work so well was the small crockpot. I didn't want the whole place to smell of my lunch (even though I thought it smelled good), but they didn't want me to keep it in my office. What worked was bringing lunch in a stainless steel thermos (preferably a lunch that wasn't very acidic). It would be better to find some insulated glass or ceramic lined container, so you don't risk the metal leaching into your food.