Effective strategies for safely interrupting play fighting in cats include using a distraction, such as a loud noise or a toy, to divert their attention. A spray bottle with water can also be effective but should be used sparingly to avoid causing fear. Placing a barrier, like a piece of cardboard, between the cats can help separate them without physical contact. It's important to remain calm and avoid yelling or physically intervening, as this can escalate the situation. Ensuring each cat has its own space and resources can reduce the frequency of play fighting.