Between about 12 months to 4 years old (and maybe further) kids are figuring out food and can be pretty picky sometimes. I have been blessed with a daughter who will eat ANYTHING and likes almost everything, but there are still tried and true foods that she will always want and hardly put up any argument to eat plus they are usually easy and portable.
This includes just plain cheese slices, string cheese, or cheese chunks. Also, cheese as an accessory. Put some cheese on anything and it is more appealing and more fun. If a kid is wary of something...try it with some cheese.
This would appear to be an extension of #1, but it is a different category. I keep soft taco sized wheat tortillas in the fridge and ALWAYS have some sort of shredded cheese in there too. You can put anything in a quesadilla and 1.) it follows the cheese rule and 2.) its instant utensil-free finger food. It's also a portable and a fun option when sandwiches are getting old. I put veggies in it, turkey, chicken, a layer of mashed beans, whatever I have or just cheese and my girl will happily eat it.
3.) Peanut butter.
Here you will get some people cringing about allergies or sugar. You can find "natural" peanut butter with no crazy extra ingredients and not much sugar. Also, there are other nut butters and seed butters you can find in most stores or health stores. Peanut butter is easy and portable and can mix with a lot of flavors in a sandwich or as a dip. Make sure your child can chew well and swallow...at 12 months just a small thin spread on a piece of toast is enough so it won't be too sticky and become a hazard.
Not the actual ones, but your own versions. If you are out and about, cut up everything in a plastic container put in some whole grain crackers and let the kids eat like that. Its not a good meal on the move (in the car or stroller) but it works at a park where you can sit and enjoy the day for a bit.
5.) Muffin Tin Meals
The concept here is to separate components of a meal into muffin tins, sort of like a lunchable, but with more options. This can be meats, cheeses, veggies fruit, sauce, and even a treat. The more colorful and fun it looks the more they will want to eat and be willing to try. This is more of an at home meal than a portable one, but it works well as an indoor "picnic" or when you just don't have time to make anything, throw a bunch of stuff in and it looks fun.
6.) Cookie cutters/Sandwich cutters.
My daughter will eat any sandwich if it is in a fun shape. There are sandwich cutters as well as just regular cookie cutters that work for this. The sandwich cutters leave less waste for actual sandwiches and save time cutting off crusts.
These are not always convenient to make but they seem like a treat and have a ton of nutrients. Put in some plain yogurt, berries, bananas, etc. and you have a pretty good breakfast or lunch. This is best when kids can suck through a straw or drink from a cup but you could do a thick one and use a spoon too. I've also seen people make smoothie Popsicle and its almost as good as ice cream. It's also a good option when kids are sick and need to eat but don't want solids.
8.) Noodles (pasta)
Especially finger food type shapes (bow tie, rotini, penne, rigatoni, fiori) When they are really little, ct them into reaaly small pieces. Later when they ae adept at chewing enough before they swallow, let the kids at it. Expect a mess but this was one of the first foods my daughter gladly fed herself. If you have kids, you know that it takes at least half an hour of frustrated feeding to get them all done. When she was able to feed herself, I was able to eat my dinner with her, or clean up a little while she sat in the high chair. Just be prepared with wipes or a wet wash cloth to wipe them down afterwards.
9.) Naked Eating and Eating Shirts
Did I mention, any messy foods would usually be eaten naked if possible? If we are at home, it's the easiest way to avoid ruining a ton of clothes. Another option is to have "eating shirts" basically a tshirt that is too big and not really fashionable (we got ours from a summer reading program that only had kid sizes not toddler/baby sizes) and it can be slipped over their whole outfit or just over their bodies and thrown in the wash . You can get some at the Dollar store too and make em cute if you want. After kids start self feeding, bibs just don't cut it. Food will end up from head to knees and in all cracks and crevices so much more protection and coverage is needed. You can also never let your kid feed themselves but then you will never be free to do anything...ever again.
10.) Hide the "good" stuff (or actually the bad stuff)
For as long as possible avoid things like chicken nuggets, fries, soda, anything super sweet or super salty. Don't dress food with extra sauces if you don't need to. Most food is tasty on its own (sweet potatoes, peas, carrots, fruit etc.) and it does not need anything added. My daughter likes hamburgers and I know its not the best option overall as a food but if we go out she will get a small burger with no mayo, no fries, and water or a very small juice box. I know if you are a new and "informed" parent you are thinking there is no way you would give your kid bad foods. Well when you are running errands and your toddler is hungry but you forgot to pack something suitable or you ran later than you thought, those drive thru's are hard to resist. You can usually get away with something less evil if you do a little research ahead. Jack in the Box has grilled chicken strips, a plain hamburger isn't too bad and has a lot of protein, most places have a grilled cheese option (though it will be really cheesy and kind of greasy.)