I've been a landlord in Ontario for 10 years and had a sublet request a few months ago. In Ontario, there are 2 stages: a tenant has to make a general request to sublet, and then a specific one. They can break the lease if the landlord refuses at either stage, but otherwise they have to provide a legitimate replacement tenant (as opposed to putting a random person forward as a pretext to break the lease) or stay until the lease ends.

Of course you could just stop paying rent and your tenancy will be terminated much faster and you won't have to go through the hassle of finding someone to sublet.

Edit: The above applies in the case of legitimate sublet request - a two week AirBNB guest wouldn't count.

The Landlord and Tenant act is the relevant law, and doesn't make any distinction between short term and long term sublets. You say you are subletting, and the landlord can refuse only with a compelling reason. There is nothing special liability wise, you are still liable for damages because you are still the one leasing the apartment.