An open idea:
Healthy juice on delivery, being a full meal on its own. There's some books and sites that have recipes. I've got a book myself, but it's in dutch, but here's an example of what I mean:
As you can see, it can for example easily be delivered in a bottle.
The why: I've noticed here in Belgium that online takeaway is used a lot, heck I used it myself a lot of times, still do from time to time, purely out of convenience.
However, all of these foods, with perhaps the exception of stuff like sushi / soup / ... are bombed with calories, tasty but not good in the long run.
And making your own juices is off course doable, but cleaning the juicer / pulp every time is a pain in the ass.
So with juice on delivery, it's a quick meal with enough good stuff in it in for the evening and it will cost less than say a full takeaway meal, which is easily around 20 euros here.
You can also easily market it by making specific juices targeted to specific wants (detoxing, energizing, whatever, add some fancy label on it). And also add some bread/meat/fish/... snacks on the side to
"complement" the juice.
And for an initial business, the only thing you need is a website and a means to promote your product, a method for delivery (car with cooling box, ...), a couple juicers and a cooling/freezing unit where you can store the juices for a day or so, dependable on the supply and demand.