I was in Jakarta a few years ago. one time a 40 min ride took 3 hours.
Lesson learned. Always pee before going on a ride but the Indo colleague said it's common for them to bring an empty bottle as you mentioned too. Then one time, he just stopped by the highway and get out, climb of the fence and started doing it as you also mentioned. So, I think no much else to try unless you want to consider adult diapers.