Here's how you should do this -
1. Add a single product in E-junkie, with the price of 21.95 and enable VARIATIONS.
2. Add three variation names - FlavorChoice1, FlavorChoice2, FlavorChoice3
3. Add the flavor list as values for all 3 and also, in the values for choice2 and 3 add a value called "none" on the top.
Once you get the button code and paste it in your website, do this -
1. Add <input type='hidden' name='amount' value='0.00'/> within the button code.
That same function can be used to do the fancy image thing popcornpapa guys are doing.
Hope this helps!