"Bread and apples"
Just '사과' without '들' can mean both singular and plural. Like '사과가 많다' (=There is a lot of apples). '들' emphasizes plurals.
According to the notes for Basics 1, "using 들 is often optional. It can be omitted if plurality is implied within the sentence, and is otherwise necessary for animate nouns/people but uncommon with inanimate nouns."
While an apple is a living thing, it's not generally considered an animate noun linguistically.
It would be 사과와 빵, since sagwa ends in a vowel, so you use wa instead of gwa.
Why is the second syllable in apple 과 (sounds like go-a) pronounced differently than the 과 (gwa) attached to bread in this sentence? Is there some pronunciation rule based on the preceding syllable?
Because in apple it isn't the "and" particle. an apple is always called sakwa
I'm not sure i understand. Is that to just say, it is what it is, no more general rule to know?
It's a different particle that's just spelled the same way, is that correct? Like a homonym?
와 is for words ending in vowels, 과 is for words ending in consonants. (Sorta like a/an in English)
The first one means "and", the second one is part of the word for "apple(s)" (and comes from a Chinese word meaning "fruit").