If you are looking for a time killer, but still engage students' problem solving and communication skills, take a look at Breakout EDU Digital version. Based on the same concept as an "Escape the Room" adventure, students must decipher several clues to unlock the Google Form.
I like that the answers cannot be found through a web search but require deeper levels of cognitive reasoning and problem analysis. I also suggest having students play in groups or together as a class with teacher participation. This allows for better intervention when attention flags or conflicts arise.
If you like the idea and want to tailor your own Breakout session for specific content areas, they also offer screenshots and suggestions on how. Be creative and have fun!
Disclosure: It took me almost half an hour to solve the easiest one by myself!