What fruit has the highest concentration of sugar?

Speaking for US produce, grapes have a very high sugar level.

Next in line come dates, Prunes, raisins, figs, mangos, crabApples, pears, passion fruit, black current

low on the sugar totem pole are:

squash, gooseberry, lemons, blackberries, youngberries, dewberries, boysenberries, graperfruit, papaya,

red currents, raspberries, Logan berries, cranberries, Elderberries

Good source for this info is:

http:/www.honeycreek.us/brix.php

or search internet for "fruit brix"

organic fruits tend to have more sugar than non-organics.