Powershell scripts for creating subsite in sharepoint online

Dahmeey Please find the code:

#Create Subsite with Unique Permission and assign permisison to it
cls
$username = "myusername@mydomain.onmicrosoft.com"
$password = "mypassword"
$cred = New-Object -TypeName System.Management.Automation.PSCredential -argumentlist $userName, $(convertto-securestring $Password -asplaintext -force)
Connect-PnPOnline https://mydomain.sharepoint.com/sites/demo/ -cred $cred
New-PnPWeb -Title "SubSite B" -Url SubSiteB -Description "Information about SUBSITE B" -Locale 1033 -Template "STS#0" -BreakInheritance
$owner = (Get-PnPContext).Credentials.UserName
#The owner will be the person provisioning the groups

#Create default groups for the new web and assign permisison
$ownerGroup = New-PnPGroup -Title "SubSite B Owners" -Owner $owner
Set-PnPWebPermission -Url SubSiteB -Group $ownerGroup -AddRole 'Full Control'

$memberGroup = New-PnPGroup -Title "SubSite B Members" -Owner $owner
Set-PnPWebPermission -Url SubSiteB -Group $memberGroup -AddRole Contribute

$visitorGroup = New-PnPGroup -Title "SubSite B Visitors" -Owner $owner
Set-PnPWebPermission -Url SubSiteB -Group $visitorGroup -AddRole Read

Hope this helps!

Please find the break inheritance and permission assign code

#Create Subsite with Unique Permission and assign permisison to it 
cls
$username = "myusername@mydomain.onmicrosoft.com"
$password = "mypassword"
$cred = New-Object -TypeName System.Management.Automation.PSCredential -argumentlist $userName, $(convertto-securestring $Password -asplaintext -force)
Connect-PnPOnline <a href="https://mydomain.sharepoint.com/sites/demo/" target="_blank">https://mydomain.sharepoint.com/sites/demo/</a> -cred $cred
New-PnPWeb -Title "SubSite B" -Url SubSiteB -Description "Information about SUBSITE B" -Locale 1033 -Template "STS#0" -BreakInheritance 
$owner = (Get-PnPContext).Credentials.UserName
#The owner will be the person provisioning the groups

#Create default groups for the new web and assign permisison
$ownerGroup = New-PnPGroup -Title "SubSite B Owners" -Owner $owner
Set-PnPWebPermission -Url SubSiteB -Group $ownerGroup -AddRole 'Full Control' 

$memberGroup = New-PnPGroup -Title "SubSite B Members"  -Owner $owner
Set-PnPWebPermission -Url SubSiteB -Group $memberGroup -AddRole Contribute

$visitorGroup = New-PnPGroup -Title "SubSite B Visitors" -Owner $owner
Set-PnPWebPermission -Url SubSiteB -Group $visitorGroup -AddRole Read

Hope this helps!