node{
 stage ("Use credentials") {
  withCredentials([usernameColonPassword(credentialsId: 'myApiTokenId', variable: 'credentials')]) {
        echo "$credentials"

        //making this call does not mask credentials
        sh returnStdout:true, script: "curl -sko /dev/null -w %{http_code} \"https://example.com/path\" --user $credentials"
        }
    }
}

[Pipeline] node
Running on master in /var/lib/jenkins/workspace/Test Pipeline
[Pipeline] {
[Pipeline] stage
[Pipeline] { (Check if test job is valid)
[Pipeline] withCredentials
[Pipeline] {
[Pipeline] echo
****
[Pipeline] sh
[Test Pipeline] Running shell script
+ curl -sko /dev/null -w '%{http_code}' https://fpajenkinstest.wdf.sap.corp/job/i856200TestJob --user myusername:4985641987298791451542
[Pipeline] }
[Pipeline] // withCredentials
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
Finished: SUCCESS