I think it is not a good idea to mix pieces of fruit with seeds and pellets, since they would rot and force you to change the food more often, in addition to not be good anymore for your budgie.
Is Yuki tamed?
A way that usually works with tamed budgies is to pretend to eat the fruit/vegetable in front of them, it is likely that they will taste it.
I don't know if it works for budgies who are afraid of humans too.
Anyway, keep in mind that fruit should only be offered as a treat on occasion, as it contains a lot of sugar.
It would be better to almost always offer vegetables, but a problem I encountered while doing so is the fact that my budgies don't like a lot of vegetables because they aren't sweet or tasty. I am still struggling with this problem.
For now I give them tomatoes and peppers, fruits that are usually considered vegetables because they are not sweet (so they don't contain much sugar), but they are tasty enough to interest my budgies.
I hope I helped you.