Sacred Tears are a Consumable Item in the Elden Ring. This is a very special item that allows you to upgrade the Crimson and Cerulean Flask Potency. Sacred Tears are almost always in churches, though not every church houses one. Here is a list of locations where you can get it
Third Church of Marika, Mistwood
Third Church of Marika mapIn front of the statue
Callu Baptismal Church, Weeping Peninsula
Callu Baptismal Church mapIn front of the statue
Church of Pilgrimage, Weeping Peninsula
Church of Pilgrimage mapIn front of the statue
Fourth Church of Marika, Weeping Peninsula
Fourth Church of Marika mapIn front of the statue
Church of Irith, Liurnia of the Lakes
Church of Irith mapIn front of the statue
Bellum Church, Liurnia of the Lakes
Bellum Church mapIn front of the statue
Church of Inhibition, Liurnia of the Lakes
Church of Inhibition mapIn front of the statue
Second Church of Marika, Altus Plateau
Second Church of Marika mapIn front of the statue
Stormcaller Church, Altus Plateau
Stormcaller Church mapIn front of the statue
Church of the Plague, Caelid
Church of the Plague mapIn front of the statue
Church of Repose, Mountaintops of the Giants
Church of Repose mapIn front of the statue
First Church of Marika, Mountaintops of the Giants