You can do as it says on the issue 1077 or as reported in this blog at noobsippets
Both suggest we do the following, and can be done on rails console:
Sidekiq.redis(&:flushdb)
Caution: This command will clear all redis records. I suggest not using it in production
another approach would be
redis-cli --scan --pattern users: * | xargs redis-cli del
according to this blog