For others (Late but worthy), I installed Jenkins via Brew, so I add Docker's path to the file below: /usr/local/Cellar/jenkins-lts/2.176.3/homebrew.mxcl.jenkins-lts.plist (Whole file looks like below)
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>homebrew.mxcl.jenkins-lts</string>
<key>ProgramArguments</key>
<array>
<string>/usr/libexec/java_home</string>
<string>-v</string>
<string>1.8</string>
<string>--exec</string>
<string>java</string>
<string>-Dmail.smtp.starttls.enable=true</string>
<string>-jar</string>
<string>/usr/local/opt/jenkins-lts/libexec/jenkins.war</string>
<string>--httpListenAddress=127.0.0.1</string>
<string>--httpPort=8080</string>
</array>
<key>RunAtLoad</key>
<true />
<key>EnvironmentVariables</key>
<dict>
<key>PATH</key>
<string>/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Applications/Docker.app/Contents/Resources/bin/:/Users/Kh0a/Library/Group\ Containers/group.com.docker/Applications/Docker.app/Contents/Resources/bin</string>
</dict>
</dict>
</plist>