I use to have 4 Iguanas of all different sizes, and I found out that they all love fresh sweat potatos the most out of all the different foods I tried. Try giving your iguana some it might really like it.
We've offered the baby food sweet potatoes a lot. They really like it and when mixed with their calcium supplements it's the best way to offer the calcium since sometimes it gets knocked of greens, etc. That way you can measure how much you give and know exactly how much they've received. We also offer a variety of baby food fruits and baby cereal as treats a couple times a week in conjunction with their fresh fruits and veggies.