As a non-American, this need to "sanitise" everything is one of the strangest cultural things about America.
I just don't get it.
As an American, for the most part, I don't get it either. It think it has much to do with advertising.
The way we stay healthy is: Eat smart, drink plenty of water, do a few no brainer things like washing our hands periodically. Maintaining the first two efforts can be tricky to do at WDW.
Along the lines the thread title is the idea of grocery shopping. We've kind of come full circle. Initially, we tried grocery shopping/packing food as a means to save money. Buying a case of bottled water offsite makes huge sense over buying it onsite, especially in summer months.
Over time, we discovered that we weren't really saving much money. Stopping at a grocery store before checking in can be a big problem, because you need to keep many items cold. If your room is not ready, baggage services will keep them cold...but there's a time factor that just gets to be too much. Leftover food? Buying groceries is only cost effective if you eat all of it. It also can take a good deal of time to drive offsite and back.
The real reason to buy food offsite is QUALITY. REAL Florida oranges are a treat!(Orange World on 192!) In season citrus is so juicy you can't peel it without making a mess!
WDW generally does not carry high quality yogurt. They sell the kind with high fructose corn syrup and thickeners. You simply can't find plain Greek yogurt.
Another thing that is very hard to find on property is quality fresh fruit: berries, pears, peaches, mango, avocado.
You can find icky iceberg lettuce salads, but that's about it.(and they are often smothered in heavy Caesar/ranch dressing) Adult entrees come with a 'veggie garnish'. It's just sad how Americans prefer to eat.
We often find ourselves stopping in the Japan quick serve because it is almost the only place on property one can get a serving of plain steamed veggies. I think they offer a mix of carrots, summer squash, green beans.
Recently, at Coronado Springs, I scoured the Pepper Market over dinner, and simply could not find nice looking veggies anywhere. Options were: ribs, greasy chicken ("roasted" but sitting is a pool of grease), a giant bacon cheeseburger + fries, cheese pizza, or Alfredo noodles! Gone was the fresh fruit/fresh salad bar!
So when we have a car, we often like to get a few healthy items on our way form the airport. it's not a money saver, but it is an opportunity to get high quality food. It may not be everyone's pick but we really enjoy the Whole Foods near Sand Lake Dr. You can get all sorts of healthy treats like fresh squeezed juices, excellent prepared seafood, tons of healthy choices from the large salad/soup/hot foods buffet. Excellent yogurt, choice fruits, veggies.