The same way most humans do, from internet. Generated data can be the result of processing yesterday's new by old model. It can be multiplied, repeated from different angles. This will make it more likely to stick in new model. But the best way is to add latest data to some storage which can act as a long term memory. In this case even old model will look fresh and up to date. I'm sure we'll get it soon. RAG can be considered as a primitive form of it.