I'm going to buck the trend here.
These bags are very cute and stylish. They are effective if you want to reduce your usage of plastic baggies. I like how they are zipper and not velcro. They do a good job, for the most part, of containing foods, although, if you're trying to store something juicy (like cut up oranges), you might be pushing your luck as the moisture will gradually seep through the seams and make the fabric outer cover damp.
If the only things you're going to use this for are dry snacks like crackers or cereal, you're probably fine just wiping the interior with a damp cloth after each use. And then once a week throwing it in the laundry for "deep cleaning".
But if you are using it for anything that is going to leave any residue (juicy fruit, oily chips, PBJ sandwiches, you get the idea here) these are really not practical. Turning inside out and wiping the interior doesn't get it clean enough for me. You can do a load of laundry (but most people don't do laundry every day) or hand wash and submerge it in soapy water, but the fabric outer takes forever to dry. So you really end up having to buy a 2 day supply of these to rotate through if you want to use them everyday. And they are relatively expensive, so buying several might be cost-prohibitive for some.
Also, the outer fabric, while cute is... well... fabric. So it can stain. Making your cute bag not-so-cute anymore. Also, it fades and shrinks a little, so the bag doesn't lay nicely after a while. Not huge deals, but worth mentioning. Your kids probably won't care.
If your looking to buy this for your kids, I would instead go with the Bumkins Reusable Sandwich and Snack Bag, Yellow, Large or Bumkins 2 Count Reusable Snack Bags, Blue/Green, Small. They are about half the price of the Itzy and for anyone who has used the amazing Bumkins Bibs, these are the same material. They are a breeze to wash, dry super fast and I've never had it hold a stain.
The prints are loud and garrish, but my kid likes it fine. Much more practical for busy moms (and dads!).
I have both the Snack Happened and the Bumkins bags, and I reach for the Bumkins every time.