7yo refusing to eat what's available

[Beachtrip]

He's gone into school today having not eaten since lunch yesterday. Wailing about how hungry he is.
Refused his dinner because it was boring (it is something he loves)
Refused breakfast because also boring (he had the choice of toast, two different cereals, granola, porridge, bread, scrambled eggs etc. But crucially.. he only wants cake, pop tarts or sugar laden cereal)

I think it's worth mentioning that at his dads they eat cake for breakfast EOW, and often go out for dinner or fill up on chocolate and treat food (I've mentioned this to his dad who says it's his time and he'll feed them whatever he wants)

I've just told the school because it's boiling hot and his PE day and he hasn't eaten for 20 hours.
He spends his evenings and mornings screaming at me about how boring and cruel I am to not feed him.
Fruit and a square meal is available whenever he wants it.
All the sugary breakfast stuff has been removed and hidden so it's not visible.
I'm at my wits end.
How long do I let this go on as it feels like it's a battle of will right now.
I can't feed Him a diet of sugar just so he eats, can I? He's got to give in and accept what's available at some point, right?
I'm looking to a) be confirmed in refusing to give in and b) any tips on getting through this.

Stick with it! Your ex sounds like a right knob. I can't face carbs(toast etc) in the morning but do like greek yogurt and a small banana.
What about one of those small carton smoothie drinks? That might appeal.

Ive always been strict with the this is what we have - eat it or not but nothing else. This is because my brother was fussy and she was cooking two different meals at least half the week. I was not going to do that! Unless there is SEN involved where perhaps I might look more carefully I would let them decide when they are hungry enough to give in.

Well done, you are doing the right thing. Maybe he is not that hungry for some reason (heat? Coming down with something?) and so just “mooching” for something nice to eat for the sake of it. In which case he’ll be fine. He’s not stashing junk food from dad’s is he?

Going against the grain here a bit but I imagine this situation around food and 2 v different parenting styles is v difficult for your DS. It sounds a bit like you and your DS are both trying to exert control over the situation. You're not wrong in pushing the healthy options obviously....but it might be better to try and find a compromise. Eg he can have x cereal some mornings...but not all.

Also are you at the other extreme to his dad? Are you trying to get him to eat super healthy / plain food. With 0 treat food... cause in most families there would be a balance. I'm not sure I could send my DS to school without any breakfast though....would he have fruit or Greek yogurt with honey for example?.

A while back when my kids were pestering for sugary treats, I googled for a picture of an person with rotten teeth - it was gross but not nightmare inducing. I explained that if you eat too much sugar this is what happens to your teeth. It worked like a dream.

Just catching up!!

Tried the gross teeth thing, no dice with my grim monsters.

No to being the other extreme. we have a good balance. The reason he was holding out is cos we had the great breakfasts available.
They in fact had waffles with fruit and honey for breakfast on Monday.

I agree this must be very difficult for him. Very confusing. And I cried most of the way to work as it went against every bone In my body to send him out hungry but the alternative was give in. And all I teach him then is if he makes a fuss he gets what he wants so it'll get worse.

He was out for a play date tonight and when I arrived he was eating grated carrot - he'd never do that at home. Cheeky beggar!

Won't touch yogurt and granola, hasnt tried it but he doesn't need to cos he KNOWS he doesn't like it. HE KNOWS.

He's a tall lad and broad, not skinny but not stocky either.

Thanks for all replies, some useful things to try.
Fingers crossed for tomorrow!!!