I have never made lunch for a 15 month old since they mostly still were nursing at that time. ( and I just would let them play with something I had, chewing on a bit of apple, or cucumber or something like that)
However, I DO have plenty experience with no microwave, we have not had one for years and years due to concerns about safety.
Any fruit or veggies, there is nothing at all wrong with beans for your little one, they are good for them. I have found most of them really like sweet potatoes or yams that are steamed, cut in big chunks, cold or not. Other ideas could include yougurt if you give dairy products and can find organic yogurt. Other veggie and fruit favorites of my children are strawberries ( with care if there are allergies in your family) peaches, nectarines, apples, carrots, cucumbers, steamed aspargus, bananas ( also use with care if allergies) blue berries, pears, and believe it or not kimchee with rice, and small amounts of white fish prepared with just a little salt.
If you have access to a kitchen but not a microwave, get a tiny pot and use it to heat up healthy home made soups for lunch, most children love soup.