If you need to pay at Azerbaijan you’ll have to use the Azərbaycan Manatı (AZN, ₼). The currency symbol is like the Euro sign but rotated 90 degrees to the right and that is not the only connection to the Euro: the Manatı notes and coins might look familiar to Europeans as they’ve been designed by the same currency designer, Robert Kalina. The Manatı is divided into 100 Qəpik and all available coins are Qəpik, the smallest note is one Manatı.
The banknotes and coins show important buildings like the Qız Qalası, the Heydər Əliyev Mərkəzi or the İçəri Şəhər. But there are also references to oil drilling, science, traditional music, literature and weaponry. At Bakı credit card usage is almost nowhere a problem. You also can withdraw money at ATMs using typical credit cards like VISA. The only case where I needed cash is paying taxi drivers.