This is not a build, it hardly even qualifies as a recipe, but it's a great tip I use intensevily during the summer. Actually my father in law just mentioned it one day, so it might not be a revolutionary new idea, but a great idea none the less.
Note: In the summer heat, they do get quite wet on the outside, so please consider using a coaster if put on furniture.
Some claim that freezing water in plasticbottles, releases dioxin, and is therefore toxic.
Just as many claim it to be a hoax, or an urban myth.
Including this guy, witch to me looks pretty credible.
Please search the internet for info, and make up your own mind about this matter.
Step 1: Recycle.
Clean and rinse, proceed to Step 2.
Step 2: Just add water...
The more water you add, the longer the cooling obviously will last.
Of course you will have less room for liquid water, but if you're near a tap, you just refill when empty, and wait a moment for it to cool.
Step 3: Freeze...
I guess if you freeze them standing, you will get slower cooling, but maybe over a longer period of time. I didn't test it.
Step 4: When cooling's needed.
Wait a few minutes.....cold drink ready.