Why don't you boys pee in the woods rather than a bottle!?
You're young, aren't you?
Thanks for the info. I've got two red. One has a pressure valve, the other doesn't. Which is best for paraffin and which for the meths?
Neither paraffin nor meths will build up a particularly high pressure in their containers, so you should be all right with either. Are you sure it's a pressure valve? No idea if the bottles are even suitable for fuel unless they're, well, fuel bottles. The red colour doesn't automatically make them fuel bottles. I have a couple of Trangia fuel bottles -- they're red -- which have a cap with a valve designed to make it easer to pour the fuel without spilling it. It isn't a pressure valve. Nice idea, but it doesn't really work so I only use them for fuels which don't leave an awful smell on things if you spill them. IMO the liquid fuels that leave the least unpleasant smell are some alcohols and the Coleman-type fuels. Aviation spirit is pretty good but you need a licence to buy it.
For water storage I mostly use the PET bottles that contain carbonated drinks in any supermarket. Little risk of confusing it with a fuel bottle, even lying flat on my face in the dark after falling out of a hammock, a lot lighter than any Sigg or lookalike and probably more useful.