It is neither a Sativa, Indica, or hybrid. The only aspect that counts when a plant is being termed a sinsemilla is that it must be feminized and unpollinated.
Times have truly changed. In the 1970s almost every cannabis farmer, as well as users, could explain something about sinsemilla.
Now, less than a quarter of cannabis consumers worldwide can give a direct answer to this question, most especially the current generation of users. They have most likely not heard the word before.
Most times, the few that have an answer say “sinsemilla is a strain of cannabis,” but they’re wrong.