It's the surface tension in your current setup that keeps the fruit flies safe. Even if they decide to party on the vinegar, they can simply fly away again and take a nice break elsewhere.
But your trap becomes a real trap if you add a tiny drop of dishwashing soap: they can no longer walk on the vinegar, but sink and drown.
Using this method, you can use a range of substances as bait, from leftover wine to fruit juice or vinegar. Ideally, you have a mixture of fruity and acidic (e.g. equal parts apple juice and vinegar), because that's what they really love. Just make sure you use not more than a small drop of soap (or touch the bait liquid with a soapy finger), because too much soap scent will deter the flies.
I know the "funnel method" is often recommended, but apparently we had particularly stupid fruit flies in the past: after desperately buzzing around for a while without finding the entrance, they usually gave up and opted to raid the fruit bowl instead.
The trap as described above works even right next to the fruit to lure them away.