Bunchy, the “only soft drink with genuine simulated gold flakes”, began in the 1950s as a small brand popular in the southwest. Originally advertised as a western-themed soft drink (and, in fact, “bunchy” is a mining term), the company re-branded the drink as a space-themed soft drink when they began distributing nationally in the early 1960s. Advertisements often featured Spaceman Jax (of Spaceman Jax and the Galactic Adventures), but other campaigns, including “America will thank you for it” and “How far would you go for a Bunchy?” were geared towards adults.
Like every profit-minded company in the 1960s, Bunchy Soft Drinks jumped on the Space Race bandwagon. Although real astronauts would have been an obvious choice for a spokesman, they were a little too expensive for this mostly-regional soft drink. Their next choice was much more animated: Spaceman Jax. He represented the excitement of space travel - saving planets in peril and defending the innocent from marauding Mantagons - without any of the danger.
Spaceman Jax was the hero with the 'heart of gold' - perfect to remind consumers of those simulated gold flakes, as ridiculous as they might seem today. As an animated character, he was part of everything that was good about the artificial world. (Better living through plastics!) Why have expensive real gold flakes in your soft drink when you could have simulated gold flakes created in a laboratory at a tiny fraction of the cost? (Why have them at all is another question altogether.) Spaceman Jax could be forever charming and funny for the simple reason that he wasn't real.
Most importantly, however, Spaceman Jax was the ideal pitchman for Bunchy because he came with a built-in audience. He was in comics and on national television, and most importantly, his audience was made up of the demographic that all soft drink companies want to reach: children. You couldn't ask for better than that.