You might experiment with dehydrating, and then powdering, said fruits & veggies and sprinkle into/onto foods they willingly eat. For example, mixing into scrambled eggs or blending into a creamy cheese.

I took mine to a Farmers market and allow them to choose. Made it an adventure.
Have them prepare the meal with me.

Fruits are overrated but just stop giving him the other options and he'll get hungry. just be inventive

You mean that going vrooommm and swerving the spoon like an airplane doesn't work anymore?

A short-term solution I've been doing with my kids lately is to play "which hand is it in." I'll take, say, 12 beans or carrots. I'll close my eyes and they hide it in one of their hands. If I correctly guess the hand, they eat it. If I'm wrong, they set it aside and don't have to eat that one. It can get a little messy with the wrong food, and it's definitely not a long-term solution, but my kids have been having a blast with it (ages 6 and 3).

And sometimes I have to guess wrong on purpose because it's too easy when my 3-year-old squeezes the green bean too hard and juice is dripping from his fingers

I used to have a vegetable garden. When I would find the zucchini that had not been found and picked early enough, and was too big and tough to just eat, I would grate it up into portions of about a cup and freeze them. Add it to spaghetti sauce, meatloaf, whatever you want. You could probably do the same thing with other veggies. Even if you're not growing them.

Make finger food fun with flavored dips of her/his choice. ...apples in caramel cubes in ranch dressing ....sliced tomato sandwiches on nut oatmeal bread with favorite spreads ....whole romaine leaves to dip in cheese sauce. ...peel grapefruit and serve sections NOT SQUIRTY HALF SLICES

I suggest to @Tati and everyone else contributing on this thread to join "Food Glorious Food". @Tati I suggest that you join "Food Glorious Food" and pose the question "Enticing children to eat a diet necessary for good health".

The group members range from beginners on the glorious path to enthusiastic cooks taught by the life of hard knocks through to professional chefs. Healthy eating to all.

I love using fruits with meat either as a sauce prepared separately or as stuffing in roasts, additions to stews and soups. Don't say what the secret ingrediants are - tomato ketchup can be stretched to include / be made of many things.

Tell him some vegetables are named after roman gladiators.... example: sparragus, zucini and broccolli.

My son was obsessed with dinosaurs so broccoli and cauiflour became trees being devoured by the mighty brontosaurus! Carrots were easy. Peas less so and green beans were impossible - not sure why.

Celery with cream cheese and raisins? Or peanut butter with raisins. Or just the sticky stuff and no raisins. I like that.

Some things that work for me:

Salads
Home pressed juices that are mostly fruity
Main dishes that smell or taste "like pizza"
Raw things w or wo dip
Cheese makes lots of ickies edible (brussel sprouts, broccoli, squash).
Brown sugar, cinnamon , nutmeg on certain sweet veggies like yams, acorn squash makes them almost desserty

I got myself to start eating more raw carrots, cauliflower, and celery by having southwest ranch dip on the side.

Set an example. Minimize junky sweets in the house. Fresh fruits and vegetables always taste better than old ones. Less salt in foods let my taste buds wake up and allowed me to enjoy the flavors of fresh fruits and vegetables. When I got into lifting and working out I realized eating more fresh fruits and vegetables would keep me healthier and help with the lifting. It may take a while. I didn't really get into eating better 'til I was out on my own but I did have all the good examples of my youth to reference. Good luck and peace.