Hi honilvin
VM Stream comes with a fairly large selection of free channels, see column 1 of the online Stream channel list << here >>
You can pay to add Sky Sports to the above channels, and will receive either a 10 per cent credit or 10 per cent reduction on your bill each month,when you pay for the Sky Sports sub through your Virgin Media bill, without having to subscribe to any other additional channels. The same applies to any other subscriptions such as Netflix, Disney+ Premium, Essential Entertainment etc that you may decide to take out and pay through your VM bill.
If you had Sky Stream then you would need to take out their base package which is the Sky Ultimate plan (Sky Entertainment channels, Freeview, and Netflix’s standard ad-supported plan) and is usually £28 a month although currently reduced to £22 a month on a 2 year contract before you can add any extras such as Sky Sports
VM have in the past offered Sky Sports for a lower price via Stream, they sometimes send an email invitation to selected customers with those offers, however I suggest that you keep checking the /virginmedia.com/tv/stream page from time to time for any offers..