City have received 6,000 tickets for the game against Premier League rivals Chelsea in Porto on 29 May.
The initiative is “designed to ease the financial pressure on fans after the impact of the Covid-19 pandemic,” a club statement read.
Because of Covid-related restrictions, the Portuguese government has said fans going to the match need to be in and out of the country within 24 hours if travelling from the UK.
The new Premier League champions have reached their first Champions League final in the club’s history.