Miércoles de Ceniza is Ash Wednesday. It is a celebration among Catholics that ushers the Lenten season. It is a period of fasting and abstinence and culminates on Easter Sunday which is another season in the liturgical calendar. It is not only celebrated in Spain but the whole Christendom as well.
Probably you thought of this because it is just the Spanish translation of the feast. It is known by other names depending on the country. Hope this helps.
A coffe as large as you want. (I prefer an Americano)
Only toasted bread with marmelade (less than usually)
A normal meal, but I recomend a Huge salad with Letuge, Tomato and cheese ( if you have more vegetables at home add them), with oil, vinager and salt. Add Salmon if you have there in the fridge.
Take a Coffe the evening has a lot of hours
French Omelette (1 egg) if you wish add tuna.
A bowl of cereals with orange juice or a yougurt.
Remember not to eat between meals.
Remenber NO MEAT. And the most important is your personal gift to God, your penitence, IT'S PERSONAL, it's YOUR FASTING MENU, YOURS...