In the mid-1970s, DC Comics and 7-Eleven teamed up to produce a series of Slurpee cups featuring DC comics characters. Here is the checklist issued at the time to assist in assembling a collection of all the cups.
There is a web page displaying images of cups featuring members of the Legion of Super-Heroes.
There are also a couple of sets of Marvel Comics Slurpee cups from the same era, but I don't have a checklist of those.