As far as I am seeing on Snopes and CBS News, this 7-Up ad was a real ad in the 1950’s.
NOTE! There is almost the same image circulating that claims to be about giving beer to infants. That is a FAKE ad. It looks virtually identical as this one, but replaces 7-Up with beer. Same baby etc.
There is also a “Soda Pop Board of America” fake ad, with the tagline, “For a Better Start in Life, Start Cola Earlier”. It also features a photo of a baby, but looks different from this. That ad is also FAKE -> Hoax Ad
They knew what they were doing
They really did! It’s the premise of the entire ad.
“Make seven UP YOURS”
“YEAH SAME TO YOU BUDDY”
“See? It’s catching on already!”
https://youtu.be/_uumprglICc