Preheat the oven to 200C/400F. Line a large baking tray with parchment paper and set aside.
In a small bowl, add your milk of choice with vinegar and let sit until it curdles, around 10 minutes.
In a large mixing bowl, add your flour, salt, sugar and baking soda and mix well. Using a 1/4 cup, add your curdled milk into it in two increments, and mix gently, until just combined.
Lightly flour a kitchen surface. Sprinkle a tablespoon of flour on top of the dough and transfer to the floured surface. Gently knead the dough, around 8-10 times, and form a dome shape. The dough should still be quite sticky. Using a sharp knife, slice twice across the dough, forming a cross shape, around half an inch thick.
Transfer the bread dough onto the lined tray. Bake for 20-25 minutes, checking around the 20 minute mark. The bread is cooked when golden brown on the tops and when tapped, makes a hollow sound from the base.
Remove from the oven and allow to cool on the tray completely, before slicing and toasting.
Notes
* Apple cider vinegar and malt vinegar could work, but it will have a very overpowering taste in the cooked bread. I have not tried lemon juice or lime juice, but I can't see it not working. To store: If you plan on enjoying the soda bread within 2-3 days, it's best for you to keep it at room temperature, in a sealed container. For slightly longer shelf life, you can store in the fridge and it will remain fresh for up to 7 days.To freeze: This bread IS freezer friendly. Place any leftover bread in a ziplock bag and place it in the freezer, as you would any other bread you freeze. It will keep fresh for at least 6 months.Thaw pre-frozen bread at room temperature, before toasting and enjoying.