- Jerry-rigged: Not really a term, but a mistaken mash-up of jerry-built (cheaply or poorly built) and jury-rigged (built with what's on hand)
- jury-rigged (built with what's on hand)
https://www.dictionary.com/e/jury-rigged-vs-jerry-rigged/
You can just use the palm of your hand over your mouth,
however to determine if you you are making progress, you make like a meter to measure your performance.
A Spirometer is an apparatus for measuring the Volume of air Inspired and Expired by the lungs : https://en.m.wikipedia.org/wiki/Spirometer
What Is an Incentive Spirometer? : https://www.webmd.com/lung/lung-incentive-spirometer
Edit add; the palm of
- Jerry-rigged: Not really a term, but a mistaken mash-up of jerry-built (cheaply or poorly built) and jury-rigged (built with what's on hand)
- jury-rigged (built with what's on hand)
https://www.dictionary.com/e/jury-rigged-vs-jerry-rigged/