Spanish Sunday is an old name for Palm Sunday in the English Midland counties, and in parts of the West riding of Yorkshire.
It’s derived from a children’s custom that flourished there as recently as the first two decades of the 20th century, and of which traces may still remain in a few districts.
A sweet drink was made for the festival from broken pieces of Spanish liquorice, peppermint or lemon sweets, brown sugar, and well-water. The solid ingredients were put into glass bottles on the previous evening, and a little water was added to make a thick, rich sediment.
On Palm Sunday morning, the children went to some local holy or wishing-well, walked round it once (or in some places three times) and then filled the bottles with its water. Almost every region had some particular spring which was visited for this purpose, and to it children came from surrounding parishes in quite considerable numbers.
When the bottles were filled, they were vigorously shaken, and as soon as the sweet sediment was sufficiently dissolved to flavour the water, the ‘Spanish’ drink was ready to use.
For more on this subject, view the thread dedicated to it on the Holy Wells & Water Lore Forum – here.