I know this won't help the OP, but for anyone with a baby or young toddler looking--- START THEM EARLY!!
Some of DS' very first foods were plain yogurt, plain kefir, and fermented veggies. He totally has a taste for sour.
The other side of the equation is to watch the sweets (even fruit), the more they have, the less they'll tolerate the sour, bitter, etc flavors.
To OP: fruit, honey, maple syrup. But do a little less and a little less (I mean minute) every few days until you get down to just a touch. If you plan to do this---don't use red (or brightly colored) fruits, they'll notice the color getting lighter!!