Pass the hat round/around
Definition 1 of 1
Pro Tip 1/3Group Initiatives
Used when someone initiates collecting money within a group, often spontaneously. 
When we realized Joe couldn't afford the trip, we passed the hat around at the club.
Pro Tip 2/3Casual Context
It's commonly used in informal settings among friends, family, or acquaintances. 
We passed the hat round during the barbecue to surprise Ellie with a birthday gift.
Pro Tip 3/3Specific Purpose
Implies that the collected money is for a special cause, not for personal gain. 
To help the local shelter, we passed the hat around at the community meeting.