Full answer
The ACV trap is the most effective DIY solution. Pour about an inch of apple cider vinegar into a glass or small bowl. Add one drop of dish soap (breaks surface tension so flies sink instead of escaping). Cover tightly with plastic wrap and poke 4–6 small holes with a toothpick. Place near the infestation. You'll see results in 24 hours.
Traps alone won't solve the problem if breeding sources remain. Fruit flies breed in moist organic matter — overripe fruit, the gunk inside drains, compost bins, wine bottles, and recycling. Remove all overripe or exposed fruit. Clean your recycling bin. Pour boiling water down drains.
Drains are the most overlooked breeding site. Fruit flies can complete their entire lifecycle in the organic film inside a drain pipe. Pour a mixture of baking soda followed by white vinegar down sink drains, wait 15 minutes, then flush with boiling water. Do this weekly during an infestation.
For faster results, commercial fruit fly traps like TERRO Fruit Fly Traps ($6–$8 at hardware stores) use a pre-loaded attractant and are more effective than homemade traps in most comparisons. They also look less messy than a cup covered in plastic wrap on your kitchen counter.
Prevention is better than extermination. Store ripe fruit in the refrigerator or sealed containers. Don't leave open wine, beer, or juice glasses out. Wipe down counters and sink areas daily. Take out kitchen trash before it ferments. Fruit flies have a lifecycle of 8–10 days — break the cycle and they're gone quickly.