Im having a peeing compeition with ym friend any ideas to make her go first read for more info?

me and my friend will be in public at a mall and drink 8 cups of liquid and none fo us can go to the toilet until 1 of us pisses our selves funny aye any idea what drink i can give her to make her go quicker or mabey a home made laxative choclate recapie she might nit pee ehr self but shel need to go to the toilet ps guys no thats gross or health concerns or anythign like that just ideas okay pps soz for typos