“Sure, I'll take whatever you have.”

You're visiting your cousin's house. She offers you something to drink. You don't know her that well, so you want to be polite and request something easy for her to get. You say:

Sure, I'll take whatever you have.

Sure

"Sure" means "yes" but is more casual and friendly.

"Sure" is also better to use when someone offers you something. When you answer "sure", it sounds like you just decided after you were offered. If you said "yes", it would sound like you really, really wanted it already.

I'll take (something)

This is similar to "I'd like ___" but it's better to use in someone's home. "I'd like ___" sounds too much like something you'd say to a waiter.

whatever you have

This means "anything". If you say "I'll take whatever you have", it means that you don't care and you'll drink anything. This makes it easy for your host if they don't have many choices.