Remember reading a post of someone who urgently needed a No.2 on a long trip, a McDonalds cola cup was in the cabin (a super sized one) and was the ideal receptacle. The consistency wasn't the best and neither was the aroma. The C172 window was opened and the offfending item was ejected.
On landing the empenage of the plane was suitably decorated in the style of a dirty protester in the H blocks.
Made me chuckle.