One of the reasons dining in a fast food restaurant is less expensive than dining in a full service restaurant is because the wait staff and services offered are less than those found in a full service restaurant.
Most fast food restaurants do not offer table side service. This means you are responsible for throwing your own trash away. Occasionally, an employee who is working in the dining room, will offer to take your tray in an effort to increase customer service when they can. If this does not happen, do not leave your trash on the table when you leave. Take it to a nearby trash can on your way out.
And by the way, if your trash doesn’t make it into the trash receptacle, pick it up and make sure it gets there. Don’t leave it on the floor where someone might trip on it.