In order to get a coupon for a free Neuro Sonic drink, all you need to do is create a new drink. That may sound daunting, but it should only take a few minutes (though you might want to make sure they sell these in your area first.)
Hopefully these taste better than the concoctions I made as a kid in buffet restaurants. I never could quite get the perfect mustard to ketchup ratio in my coke. And don’t even get me started on how much pepper you had to add before you could taste it!