There should be a lid (usually saran wrap with some super small holes for the bugs to fly in, but not out, of) on the apple cider, or they won't be trapped.
Also, look at your garbage disposal policies. We were getting a hole lot of fruit flies until we started keeping banana peels and other food scraps in the freezer. (I empty the small bin into the appropriate outside receptacle whenever it is full.)
Finally, check your houseplants. Sometimes they have disease or decaying leaves which can maintain small insect populations. Depending on the type of plant, you can repot into clean soil, give them a serious shower, or throw out entirely.
| Pounds lost: 73.0