Obviously if you have lost your job, been furloughed or otherwise have an income problem, you use that check for necessary expenses to keep your family going.
However, if you have your income, what do you do with the money?
My suggestion, save it for a future rainy day at least until the crisis is over. Stimulus implies spending it to help the economy, but if you do that you may create your own financial crisis in the months ahead.
And remember, if you had a increase in income since 2018, you could be required to pay all or a portion of the stimulus back. However, there seem to be questions about this actually happening.