I take it you sprayed the entire fig tree with it then. It would have been better to just simply apply some of it to just the trunk area of the tree, thus stopping the ants from crawling up the trunk and getting on the leaves-----if that homemade concoction would work anyway.
You don't say how big the tree is, but I'm assuming it's still pretty small. Fig trees are hardy and if all the leaves yellow and fall off, I'd think it would recover and set new leaves. First thing I'd do is wash off that concoction and hope for the best.
I had a mature fig tree when Hurricane Katrina hit New Orleans and it was under salt water for 2 weeks and then for even longer in fully saturated ground and it survived and actually thrived not long after it began putting out new leaf growth the following year.