Oh my gosh, I feel your pain! I have a 7yo DS who has sensory issues and is very stubborn about trying new things. The older he gets, the worse it becomes. I've tried withholding food, bribing, explaining about good health, cavities from junk food, begging, sneaking it in, you name it! I'll tell you what we're doing now that is working REALLY well.
I created a daily health food chart. My children and I write down what they eat each day, and they get one point for healthy food choices and 1 negative point for unhealthy choices. We count up the points and at the end of each week, they get fake dollars to spend in my "mommy store". They LOVE this and it's been working really well- additionally, as we put the foods in different categories, I always explain why something is or is not healthy, and what it does for our bodies so that way they understand. I wasn't too keen on the idea at first, but I was so tired of DS eating nothing but bread and pasta all the time- now he's making a concious effort to get his fruits and veggies in, and is very proud. Eventually, once I feel that he's making good choices regularly, we plan to phase out the chart. Just an idea!!
Previously, his typical day consisted of the following, despite healthy options being offered at each meal:
Breakfast- oatmeal
Snack- none, because at school they only serve fruits and veggies
Lunch- pb&j sandwich, crackers or cookies, fruit snacks, etc...
Snack- fig newtons, cookies, anything carb-a-licious
Dinner- macaroni or spaghetti, refused to eat meat or veggies with dinner
Today he ate the following:
Breakfast- unsweet cereal with almond milk and a banana
Snack- watermelon and apple slices
Lunch- sandwich with sunbutter and honey, applesauce, cheese stick
Snack- pb crackers on whole wheat and a banana
Dinner- macaroni and cheese (organic rice pasta) with peas
He still won't eat meat, but that's no big deal at all to me (I grew up vegetarian and am fine with finding other protein sources for him). SO we're doing better, not great, but I'm hoping this works long term. It leaves my kids in charge of their own decisions, which I like.