Make the syrup first by combining sugar, water, lemon juice, cream of tartar, cinnamon, and ginger in a saucepan. Bring to a gentle boil, then simmer for 2–3 minutes. Cool to room temperature and refrigerate overnight or freeze for 2–3 hours.
Mix flour and salt in a bowl, add yogurt, and stir until combined. Knead gently for 2–3 minutes until smooth.
Roll the dough to ⅛ inch thick, cut into strips, and braid them. Pinch the ends to seal.
Heat oil to 350°F / 175°C and fry the koeksisters until golden brown, about 2–3 minutes per side.
Dunk the hot koeksisters in the cold syrup for 30–60 seconds, then let the excess drip off.
