Open your app's Documents folder on iOS simulator.

appdocdir.zsh

function myappdocdir() {
    devid=$(xcrun simctl list devices | grep Booted | sed -n 's/^.*\([A-F0-9]\{8\}-\([A-F0-9]\{4\}-\)\{3\}[A-F0-9]\{12\}\).*$/\1/p')
    for folder in ~/Library/Developer/CoreSimulator/Devices/$devid/data/Containers/Data/Application/*; do
        if [[ -a $folder/.com.apple.mobile_container_manager.metadata.plist ]]; then
            if [[ 'com.apple.phone' = $(/usr/libexec/PlistBuddy -c 'Print :MCMMetadataIdentifier' $folder/.com.apple.mobile_container_manager.metadata.plist) ]]; then
                echo $folder
                break
            fi
        fi
    done
}
alias cdapp='cd $(myappdocdir)'
alias openappdir='open $(myappdocdir)'

Put these code into your .zshrc.
Replace com.apple.phone with your own's bundle ID.