I don't have a lot of experience with having to carry my lunch, only 30 years.
What worked best for me was the hard plastic Gott six pack coolers with the re-freezable water bottle that has a plastic screw that attaches the bottle to the lid.
I have 3 bottles. I would usually put the one "on duty" in the freezer when I got home and the other two were ready when needed, the third was on standby for when I forgot or had to go right back out. You can always drink the water too if your jug gets low or dry. Change the water regularly and always use good water. I usually carried a small frozen bottle of water in the box too. Seems like there was never too much water to drink.
My first one only lasted 23 years and then petered out. Had it's replacement in the shop from a garage sale for $2.
I don't know if they are even available now, probably not as they worked too well. Regards, FM