Coffee is important!!!
There were definitely some days when there was no coffee first thing in the morning. If you need your caffeine first thing, you might want to carry a coil or instant! But there is coffee somewhere each day!
The day over the mountain to Segovia, I knew there would be no coffee when I left, so the night before I bought one of the now ubiquitous cans of cold coffee that you can get in stores. Definitely not ideal! But it was caffeine and then the proper coffee in Segovia in the afternoon was all the better.
The biggest surprise was leaving Segovia on a Saturday - maybe around 8:00 - and not finding any coffee in the city. Nor was there any coffee in the first village you come to up the hill (where the bar opens late on Saturdays. I think I was there around 9:00). But - a nice surprise - there is a small coffee stall in a park in Valseca. People on the street showed me where to go - it is about 5 minutes off the camino. Coffee was really good and the people there were very friendly (someone bought my coffee for me). It is on google maps -- Chiringuito Valseca in the Parque Municipal.
Santa Maria - first coffee was in the hostal Avanto where I stayed. Second coffee in Nava. Nothing was open on a Sunday morning in Santa Maria itself. It might be different on weekdays.
Coca - first coffee at the bar where you return the key. Second coffee not available until the end of the day's walk in Alcazaren.
No coffee in the morning in Alcazaren. First coffee in Valdestilla, where there are at least two bars.
Puento Duero you will be able to get coffee in the albergue. There was also coffee in Ciguñuela.
Penaflor, for me, was a bust in terms of dinner and coffee. No food in town (no shop) except a bag of chips available at the one bar (of two) that was open when I was there (I think it was a wednesday). No shop. No coffee the next morning.
Excellent first coffee after Penaflor in Castromonte (but no food).
In Valverde de Campos (after Castromonte) - there is a bar that is open in the morning, but only for a few hours....However, there is a man, who works for the village, who will come and open the bar for you - if he sees you! I was sitting on a bench in a square across the way, eating my lunch, and he came and asked if I would like to have something to drink at the bar. Super nice. The bar is also a small shop.
Medina - lots of coffee!
After Medina - There is apparently a bar in Tamariz, but it was not open when I walked by.
Cuenca - good bar/restaurant in afternoons -- not open first thing in the morning. There will be coffee available in the albergue in the morning when you leave. And Villalon is only about an hour away with lots of bars.
Santervas - there will be coffee at the albergue in the morning. After Santervas there is a tiny pueblo where there is a bar -- it was not open when I walked by - but there was someone there cleaning and she asked me if I wanted a coffee.
Next option would be Grajal. Or just keep going another hour to Sahagun.
The day of the week makes a real difference. Three days in a row I ended up in villages on the days that their bars were closed. My advice: don't start your walk on a Tuesday! (if you are doing the standard etapas)