Rex is packing a Saturday picnic. He knows the food. He does not know some and any.
What they mean
Both words talk about an amount, not an exact number. You use them with plural nouns and with uncountable nouns.
I have some apples.
I do not have any juice.
We need some bread.
Is there any cheese?
The picnic plan
You can say I have apples. Adding some tells the other person there is an amount — not none, and not a counted pile.
The next pages split the work: some when you have it, any when you do not, or when you ask.