Best time to take an OPK

Bee
Hi all
I'm confused about when's the best time to take an OPK. Some say any time, others say after 11am, then some say opitimum time is about 2pm. 
The longest I go without a drink is overnight, so my first wee in those terms would be best. However I've read that LH might not show at that time.
Would appreciate any feedback!