Informal:
* "I'll pop in later this afternoon to see how you're doing."
* "I just wanted to pop in and say hello."
* "I popped in to the store on my way home from work."
Formal:
* "I'd like to pop in for a brief meeting on Friday afternoon."
* "I'll pop in during my lunch break to discuss the proposal."
Other examples:
* "I popped in to see if you needed anything from the shop."
* "I'm just going to pop in to the bathroom."
* "Do you want to pop in for a drink after work?"
Note: "Pop in" is a very informal phrase. It's generally used with people you know well and in casual situations. You wouldn't use it in formal situations like a business meeting.