There are 2 issues:
Try like this
$script = "sed -i 's:^IPADDR=.*`$:IPADDR=$($IPguest):g' /etc/sysconfig/network-scripts/ifcfg-ens160"
Invoke-VMScript -VM CentOS-7 -ScriptType bash -ScriptText $script -GuestUser root -GuestPassword P@ssw0rd
Blog: lucd.info Twitter: @LucD22 Co-author PowerCLI Reference