I just think its funny that you are pointing out they are in Mt Dew bottles, like I didn't notice.
"Oh, oh my, I had no idea!"
Its just left over containers from when I started my tomatoes early this spring. I had like 30 plants and I just saved all sorts of containers.
Once the roots are sticking below the net pot a few inches, I'll move them to 5 gallon buckets. But since you have to swap out the nutrient mix every week or two when doing DWC, I just didn't want to waste any. I've already burnt through half of my 25lb order of masterblend.