ENV JAVA_HOME /path/to/java

task createDockerFile(type: Dockerfile) {
    destFile = project.file('build/docker/Dockerfile')
    from 'openjdk:10-jdk-slim'
    addFile "./build/libs/MyRestAPI-${project.version}-SNAPSHOT.jar", "MyRestAPI.jar"
    runCommand 'sh -c 'touch /MyRestAPI.jar''
    exposePort 9080
    entryPoint 'java', '-jar', '/MyRestAPI.jar'
    ENV 'JAVA_HOME /opt/jdk10'
}

unexpected token: JAVA_HOME @ line 54, column 9.
         ENV 'JAVA_HOME /opt/jdk10'
             ^