How a swamp cooler works:
The evaporating water in the swamp cooler draws away heat making it cold inside. The fan draws the cold air out of it, cooling surrounding areas. The warmer it is in the room the cooler it blows.
-Computer fan = $5
-9v battery = $1
-Popsicle sticks (8 or so) = free
-Plastic Bag = free
-Glue sticks (Hot glue gun) = (5 pack) $2
-Water = free
-Switch (optional) = $2
-Hot Glue Gun = $5 -10
Step 1: Standing the Fan Up
Glue 2 Popsicle sticks one each corner, it provides the stability you need. If your wires are very long make sure to wrap your wires around a little bit so you don't have to cut and splice.
You can trim the tops if you want to make a cleaner look.