Soda Pop Bottle Rocket Boosters! Cheap and fun! Paint two 2-Litre soda bottles w/silver spray paint, hot glue them together when dry and add felt "fire" with Hot Glue, and Hot glue them to a small backpack. I picked up one for a Dollar at Goodwill. This will be a go to for all of the kid Cheap and Fun. I use these as birthday party gifts now too!