I can not recommend this @yumboxlunch lunchbox enough! It helps me pack healthier lunches, I don't have to fiddle with baggies or containers and lids, and it has a watertight seal so I can put yogurt or apple sauce or soup or ranch dip in one section and it won't spill to the other sections.
The side on the left is large enough to fit a sandwich, or you can do 2-4 silicone muffin cups to make your own dividers.
It's dishwasher safe and has held up great after a year of use. .
This is the panino style but they have other sizes and colors as well (ones with more sections, that are snack sized, or adult sized)
You can buy them from their website, Amazon, or other retailers.
What are some foods that your kids like in their lunches?