TCDD offers economy/business classes only in high speed trains.
Economy class offers 2+2 seats. Half of the seats are in one direction, and rest in other direction. In each car, CAF sets have 4 tables and Siemens sets have 2. 4 passengers seat around one table.
Each wagon has one WC, space for big suitcases and luggage area over seats.
Four and a half of the six cars of CAF sets and five and a half of the eight cars of the Siemens sets are sold as economy class.
In CAF sets, there are only electric plugs under seats which are next to tables.
Some of the economy class wagons may be sold as “economy class + refreshment” depending on the route and time. That means passengers would pay TL 20 (€ 5) more compared with “economy class” and get a free meal during travel (as of January 2018). Economy and economy+refreshment wagons are separate. You need to find seat from the option you want.