빵 먹고 커피를 마셨어요. ate bread and drank coffee. has same meaning as with.

It would be "커피와 함께 빵을 먹고 있어요" literally, but "커피에 빵을 먹고 있어요" would be more natural.^^/ \^o^/

빵은 먹다 커피는 마시다 하지만 마시다를 먹는다라고도 표현하니까 빵과 커피를 먹고있습니다. 라고 하면 될 듯

If you wanted to say "with" as in "with someone you did something" you would say 진구 하고 함게 했어요. or 진구 하고 같이 했어요. I'm not sure if you can use 와/과 in this instance, because I usually only use them for objects or with lists.

빵 ends with a consonant so you would use 과 instead of 와. And you dont eat coffee so you cant say I ate coffee with bread. 먹다 -to eat 마셔다 - drink