"These sandwiches are tasty."
Translation:Te kanapki są smaczne.
Accidentally your sentence makes some sense, with another meaning of "to". Imagine that you see sandwiches, milk and cheese and someone tells you that only one of those things is tasty. "To kanapki są smaczne" means something like "It's the sandwiches that are the tasty ones". Of course it's not a very likely sentence.