Welcome to ATP, Mahario.
>> the initial idea was to combine a cucumber and watermelon
Wow, major league! Those are not just different species, they are from different genuses (genera)! Cucumis and Citrullus.
Maybe those are prone to inter-breeding and I just don't know it. It sounds like a big challenge to me.
>> meant to entice children to healthier eating
A noble goal, but an uphill struggle. My thought was "bred those cukes for a disgustingly high sugar content", but then you said HEALTHIER eating.
I suspect that the only way to get kids to eat what they SHOULD, instead of what rots their teeth, is the method that I think the mainland Chinese are using to get their people to ever EAT all the GMOs they are inventing and stockpiling.
At some point, there will be a famine or food prices will go through the roof due to drought and erratically changing climate. At that point, the Chinese government has a very persuasive argument":
"Eat this or starve".
That would do it.