Selena signed with Coke when she was 18. She was spotted by a Coke representative (Bonnie Garcia) in 1989 at the Tejano Music Awards. At her graduation not long after she was presented with the endorsement check for $50,000. She was one of the very few artists that coke kept in the '90s. They were using regular actors in their commercials, not celebrities but were expanding their Latino marketing department. Selena made 3 commercials for coke her first in 1989, second in 1991 and third in 1992. She also recorded a radio commercial and the music sounds very similar to Baila Esta Cumbia. Chris also mentioned working on this in his book. I've heard the commercial but I don't have a copy of it. Most of her promotion was pictures, coke discovered that she was a great cardboard cut out and that is how they used her image.
In1994 to commemorate her 5th year with them they ran a special ad and released a special edition bottle. They also had a special promo poster featuring an autograph ready to be released in 1995 but when she passed away they ordered it destroyed. Someone who worked for either the printing company or coke snuck a box of them out and they were available on eBay. I am lucky enough to have been able to get one.