I invented something at the dog park the other day.
Our dog park was designed by someone that doesn't use them, and maybe doesn't even have a dog. Probably a cat person. Not that that's bad but they shouldn't be put in charge of the dog park.
I have a big orange backpack that I cart a gallon of water and a water bucket in when we go since there are no water dishes and no water source.
Anyway I designed a disposable water dish that hangs on the fence out of a gallon milk jug (they throw anything away that is left in the park).
I sliced the handle 3/4 of the way down and cut a big hole in the front, all the way up to the spout and out through the sides so they can get their big heads in there. I think I will cut the next one (this one has already been thrown out) so it dips down a little more in the front since it hangs at an angle and the water level is lower at the front. Don't cut the handle off, just slice through it so it keeps the dish from being knocked off the fence.
Why hang it on the fence to begin with? Because some dogs like to dig in them and splash all the water out and the others just knock them over.