You're going to need a drachma - a Greek coin.
Fortunately there's one nearby
In the sewer just outside the bar, the item sparling behind the sewer grate is the coin you need.
If you try to climb up the fire escape in the back of the bar, you'll end up with a long slender pole.
That fits through the sewer grate, but there's no way to make the coin stick to the pole.
COMPLETE SOLUTION IS NEXT
Use the gum from the tourists on the airport on yourself. You'll end with a wad of gum. STick that to the end of the pole, and use that on the sewer grate to get the coin.