Best way to carry home groceries on a motorcycle?

7 miles is within your comfort level huh? I think you're full of it. And after looking at your questions, i'm sure of it.

A buddy of mine had a Honda Goldwing and now has another comparable bike, but he uses containers that already came on the bike as well as added some additional ones. He's able to carry a lot currently, actually furniture using straps, but yes, he can put an okay amount of groceries in those. Depending on the size of your bike, it could be doable without looking too bad. For something light enough and not too crazy perhaps a backpack can work.

A decent hiking pack will hold over 40 kg of groceries.

Mind you if 7 miles is as far as you feel comfortable riding I'd suggest you either give up riding or buy a more comfortable bike - ie a standard. or a tourer.

You can sit the box of wine on your legs, hunch forward a little and force your elbows down to keep the wine from slipping off the side. Try to pick a route that does not require many turns. You may have to make a separate trip for the cheese puffs. The licorice whips will fit in your pockets if you don't get too many.

I put my heavy shopping in a rucksack on my back. Use and extending tank bag for bread and lighter/softer shopping. I take off the cowling and put the passenger seat on and cargo net all other stuff, like my horse's carrots, apples and my vegs.on that. I have a GSXR 1000K3

To be honest your only option would be soft panniers/saddle bags or a ruck sack for the wine? Better would be hard Panniers and Hard top box for the Liquorice Whips, Although they could go in a soft tank bag?

Use a backpack, like a book bag that kids wear to school to carry their books and other personal possessions.

Bigger saddle bags or buy a mini trailer designed to be pulled by a motorcycle.

You don't. Think of how many episodes of "Happy Days" where Fonzie bought groceries and used his bike to take them home.

Well the troll versions of wine, cheese, licorice whips, ect are pretty small. You can probably just throw them in the saddle bags, should fit about a years worth.