Even better (for men), Transfix incontinence condoms. Roll on, attach to pee tube (either routed to outside the glider or to a suitable bag), and no hassle, no chance of leaks.
Several litres of water in a Camelback, direct connection to the outside world - all sorted. No chance of dehydration. No danger from field landings with a full bladder. Seriously, getting this sorted out is a major flight safety issue.
When phoning up to buy some of the above, and wanting to pay, rather than charge the NHS, I was asked "are you a glider pilot or a diver?" Everyone else gets them free.