Sardines is a hide-and-seek variant. One person from the group hides, and after 15 seconds, the others go and find them, joining them in the hiding spot as they find them. After everyone has found the hiding spot, a new hider is chosen and a fresh round starts.
Rec Room Mini-game Monday - Sardines
Video of Sardines by Mamamonkey
Rules can be varied, but generally there are two rules which make the game more fair: no hiding inside objects such as walls or rocks (leaves and grass are ok); and you need to be able to teleport to your hiding location.
Recommended maps for Sardines are Clearcut, Spillway, and Homestead. Don't start a paintball round as it will move the hider out of their location!
Recommended settings for Sardines are Teleport Bubble: Small, Ignore Bubble: Off, Show Names: Off, and Microphone: On.