<font face="Verdana, Arial, Helvetica, sans-serif" size="2">I recently flew a 14 hour flight in coach. At the end of the flight, as always, everyone gets up and goes to the restrooms, and so do I.</font>
For males, an empty water bottle works fine, especially if you're discrete. Women can also learn to do this.
http://www.restrooms.org/standing.html