create a file in config/initializers called bust_cache.rb with following contents:
ENV["RAILS_CACHE_ID"] = 'version1'
If in future you wish to bust the cache again change the value to 'version2' etc. If you wish to bust the cache with every deploy use:
ENV["RAILS_CACHE_ID"] = Time.now.to_s
***Note that this last strategy will not work with multiple dynos on Heroku or other such similar situations
thanks to Nathan Kontny