This is an unusual Czech Marianske Lazne spa sipping cup, with integral sipping straw.
 
A Czech Mariánské Lázně spa sipping cup is a specific type of souvenir associated with the famous spa town of Mariánské Lázně (also known as Marienbad) in the Czech Republic.
 
Mariánské Lázně is renowned for its natural mineral springs and has a long history as a European spa destination, attracting visitors since the 19th century.
 
These cups are designed for drinking the mineral-rich water directly from the springs, known for their therapeutic properties.
 
The unique shape includes a spout or straw-like feature attached to the handle, allowing visitors to sip the water while walking around the spa town.
 
It is stamped R on the base.