Personally I would have done one of the following
Gently slid off my seat not raising anyones attention, commando crawled through all the popcorn, discarded sweet wrappers and empty cups smiling as I went knowing I wouldn't have to watch it any more.
I'm over 40 so falling asleep in social situations isn't an issue
Feign a stomach upset and dash for the toilet and sit in the cubicle watching lol cat clips on youtube.
Spend the whole movie taking the mickey out of everything I can.
Gently slid off my seat not raising anyones attention, commando crawled through all the popcorn, discarded sweet wrappers and empty cups smiling as I went knowing I wouldn't have to watch it any more.
I'm over 40 so falling asleep in social situations isn't an issue
Feign a stomach upset and dash for the toilet and sit in the cubicle watching lol cat clips on youtube.
Spend the whole movie taking the mickey out of everything I can.