Hmmm... well I do have one suggestion that could work... actually a few.
If you know any friends/family that have access to hydro/water, bring a kind donation from the local LCBO or Brewer's retail (just kidding.. haha).
In cases like that I would recommend using the local self-serve coin wash. For the first cycle rinse the vehicle thoroughly and before the cycle runs out fill up your bucket with some water (of course, make sure you bring a wash mitt, chamois/equivalent drying accessory, soap, etc with you ahead of time). Once the cycle is finished, wash the vehicle by hand and purchase another cycle to rinse. Finally, dry the vehicle and dress your tires, etc. Also: do not forget to clean your rims off during the first cycle.
This should be sufficient for cleaning the vehicle given the circumstances however, I would not recommend doing this at the local self-serve wash when you have a huge line up of people waiting for their turn. Doing so in a case like that may result in numerous odd looks and an assortment of unfriendly hand gestures from people waiting in line.
