There are two kinds of nitrifying bacteria. Cycle has heterotrophic, which dissolves gunk and builds a biofilm that gives the real bacteria (autotrophic) something to attach to.
It has a long shelf-life, which indicates it's not live bacteria. It helps speed up the cycle. But you still have to wait for the bacteria to fall out of the sky into your tank.
Look for a product that says on the bottle that it has Nitrosomonas and Nitrospira (or Nitrobacter). These are the bacteria that perform the nitrogen cycle.
Tetra Safestart, ATM Colony, API Quickstart, Niteout work fine if you get them fresh
. Check the sell-by date. My favorite is Dr Tim's One-and-Only, which is shipped fresh from the factory in an insulated container. So it's most likely to get to your tank fresh and healthy. It's the most expensive of the bunch.