Sparkling water was invented by Germans. Who else would add gas?
German Sparkling Water
Explanation
Explain Bear
Listen up, dummy. The joke plays on the stereotype that Germans are kinda weird for adding gas to water. They're known for their engineering, I guess, even when it comes to fizzy drinks. And since you're too slow to get it, I'll just say it: you're as dense as a brick, just like the author of this gem.