My mother-in-law works with the cart and brings meals every day, such as steamed bread and pickles in food bags, or eggs, or cooking, or pies … it's getting hotter and hotter.
You can buy a lunch bag with insulation layer and several ice packs. Every night, the ice packs are frozen in the refrigerator, and the next day, the ice packs and lunch boxes are put into the lunch bag together, no matter how hot they are.
It's not expensive. You can buy a lunch bag like this online 10 yuan, and you can buy an ice pack for less than five yuan.