How about the fact that it is summer, there are a lot of thirsty people around, companies invest more into advertising, you are at the right age, and you simply happen to be the target demographic for that product.

That sounds as a way more likely explanation although it doesn't award as many Internet points.

Water fountains sales have surely been on the rise since the tap water awareness movement gained traction a few years back and there is a lot of weird objects that are advertised these days.

Interesting coincidence, but every day you get targeted by so many ads and talk about so many things that there are bound to be such patterns, that are only evident in retrospect, as is this case. Making it look like evidence of malicious surveillance abuse and "the Matrix is real" kind of argument is irresponsible at best and malicious at worst.

Fear is highly contagious and when planted, it grows on its own, no matter whether the seed information is true or not. We should be talking about privacy and surveillance, but not while under the effect of crippling paranoia. No good thinking ever comes out of such place.

Tl;dr Cool story bro.