Pressing and holding a message then taping delete will remove the Snap message on both sides. Snapchat will eliminate it in both conversations, yet the other user will be able to notice that something is deleted until it was not watched.
To delete a Snap message on both sides, press and hold the message, select Delete, then confirm. The message will be removed from both your chat and the recipient’s chat, though they may have seen it before deletion.
Pressing and holding a message, then selecting Delete, then confirming is used in order to delete a Snap message on both sides. The message will be deleted by the chat and that of the recipient, but they might have read it before being erased.