I have done this before - you will need two colors of 5inch balloons and then a 260 and another to make the candle. 260 scraps will make the sprinkles
make a small sand weight first using an 11inch or 9 inch balloon - 5 inch balloons are to lightweight. Make it the size of a golf ball.
This really is just making garland. Using the cake color blow 10 of them up to about 3 inches. I use 5 in each row instead of 4 since it makes it more round looking. Tie 3 balloons and the neck and then 2 and then put those together to make the five. Tie the the sand weight to them. It will probably not sit flat yet, make the next group of five. Then using the frosting color, make a group of five - blow them to about 4 inches. Once more group of five blown up to 3 inches. Then use a cooridination 260 and just stack them like you are making garland. Blow up the 260 you are using as the candle color about the height you want. Use a 5 inch that you want as the flame color and marriage twist it to the candle, then tie the other end to the top of the cupcake so it sticks straight up. Use rubber cement to glue 20 sprinkles on the top...
I cannot put a picture in a post here to save my life - but here is the link to a pic of one I did....http://www.flickr.com/photos/bamaballoons/3978556446/