I sprained my ankle and was told to wear an air cast for the next week. it doesn't fit with my sneaker should i just not wear it at work?

Not a good idea: It's probably not a good idea especially if your job requires you to walk or stand for prolong periods of time. Treatment for ankle sprain is RICE (rest, ice, compression, elevate leg). You may want to ask your doctor for a "post-op" shoe which may allow you to wear your air cast or ask if a different compressive ankle brace is available.

Depends: It depends on how your ankle feels. Early mobilization of ankle sprains reduces the duration of symptoms. If you are able to walk on your ankle with minimal discomfort you might try forgoing the splint. If it is still really painful, you will want some type of support to help you make it through the work day on your feet. Remember to take breaks and elevate and ice your ankle throughout the day.