This won't fit on a water battle, but it doesn't take up much space.
Flatworld Orikaso Cup

http://www.rei.com/online/store/ProductD...vcat=REI_SEARCH

This will fit on the bottom of a 1 liter Nalgene (or similar) bottle
Olicamp Space Saver Cup
http://www.campmor.com/webapp/wcs/stores...p;amp;langId=-1
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"Sometimes, it's better to be lucky than skillfull"