Dish soap without the H2O!
Make Nice Company's answer to zero waste cleaning products is here; the small dish bar will replace 3 plastic bottles worth of liquid dish soap and the large replaces up to 8 bottles worth!
Rub the dish bar with a scrubber or cloth to create suds and then get right into your dishes.
Rinse well between uses.
Drain run-off water from soap tray after each use to prolong lifespan.