Get vars in Jenkins Pipeline
If you want to use environment variables with the ${VAR} syntax in the declarative pipeline, then you need to define those variables in the environment { } block.

for example:  

environment {
        DISABLE_AUTH = 'true'
        DB_ENGINE    = 'sqlite'
    }

    stages {
        stage('Build') {
            steps {
                echo "Database engine is ${DB_ENGINE}"
                echo "DISABLE_AUTH is ${DISABLE_AUTH}"
                sh 'printenv'
            }
        }
    }



If you want to use environment variables that come from other plugins etc, then you need to access them with the env.VAR syntax.  For example:

echo "Running ${env.BUILD_ID} on ${env.JENKINS_URL}"