Oh, subliminal messages......
https://www.cbsnews.com/news/the-10-best-subliminal-ads-ever-made/
I studied subliminal advertising in college and I remember a few of these! But, like whoever wrote that feature, I always wondered why that would be particularly effective. I mean who runs out for a beverage because they subconsciously notice the word "sex" in the ice cubes? I remember several other ads like that -- where naked bodies or, in one case, a skull, could be seen in the cubes, and another one where the big capital letters were shown reflected in liquid that made them look like they said S-E-X. (I'm trying to think what they were -- CFV? The F and V could reflect as E and X, but the S would be all twisted. Still, maybe it was close enough.)
Another method I remember reading about was to flash single frames with pictures of Coke during the commercials or trailers before movies -- the eye wouldn't really register it but the brain would. If that's actually how the eye and brain would work, I can see that being effective.
But I bet the most effective are the ones that are recocognizable enough to draw controversy and attention. Remember that ad from a few years ago -- I can't remember the name of the fast-food chain but the ad was a picture of a giant elongated sandwich aiming into a shocked-looking woman's wide open mouth? A lot of people hated that one, of course, but I'm sure it got attention for the chain and probably some business.
The other day I drove past a tow truck from "Kamel Tows -- the best tows are Kamel Tows!" That one was kind of gross. If I'm getting my car towed, that name, memorable though it might be, is not going to be a big draw.
But I remember a butcher shop in New Orleans with the slogan "You can't beat Wagner's Meat!" I thought that one was a bit more subtle and humorous. Plus it was New Orleans, where people like controversial things if they're funny.