"The teacher drinks coffee."
Translation:Öğretmen kahve içer.
Notice, it does not say "The teacher drinks the coffee." The accusative is only used for specific direct objects :)
Içer means the teacher drinks( as part of routine) while içiyor is the present continuous which means the teacher is drinking coffee
If it were "The teacher drinks THE coffee," would 'coffee' have to add a suffix: maybe 'kahvesi'???