What you'll need...
1 bottle of vodka (see above)
1 bottle of carbonated "sparkling" lime water (usually sugar, caffeine and sodium free!)
Lime slice for garnish
Get yourself a cup... any cup. If you're on vacation in a cabin, a coffee cup will do just fine. :) Put some ice in it. Add a shot (@2-oz) of vodka. Fill the rest of the glass with sparkling water. Add a slice of lime. The limes serve double duty... they add a little extra flavor and they also serve as markers to how many drinks you've had. Just add a new lime slice every time you refill!
You could use any flavor of sparkling water you like and an appropriate fruit garnish.