Benjamin Glynn, 40, was found guilty on four charges of breaching coronavirus protocols.
Glynn, who represented himself in court, was accused of causing a public nuisance and using threatening words towards public servants.
He was earlier subjected to a psychiatric assessment ordered by the judge as a result of his conduct and remarks in court, according to local media outlet CNA.
He described the charges as "unlawful" and asked for his passport to be returned so he could return to the UK to be with his family,
The judge told Glynn he was "completely misguided" in his belief he was exempt from Singapore's laws on wearing masks.
The city-state is well-known for its enforcement of strict rules.
It is mandatory for everyone aged six and above to wear a mask outside their home.
Singapore has jailed and fined others for breaking Covid-19 regulations throughout the pandemic.
Some foreigners have had their work permits revoked for rule breaches.
In February, a Singapore court sentenced a British man to two weeks in jail after he sneaked out of his hotel room to meet his then fiancée while in quarantine.