HTTP body variable set, but how to make random data in test case

i would like post different API body every time the test case run.

i have set the variable at POST object
e.g. testID default value test0001
then the HTTP body as below, test and verify passed.
“drugId”: “$testID”,

what syntax/command i can use in test case like parameterize test step, so first time test case run
drugId = test0001
second time test case run, it will be
drugId = test0002