In a large bowl, whisk together flour, sugar, and salt. Gradually add milk while whisking (or mixing with a hand mixer). Follow with water and mineral water, continuing to whisk until smooth. Now add the eggs and mix until fully incorporated. At the very end, use a spatula to scrape any flour from the sides of the bowl, and mix it in, to avoid potential crumbs. (If necessary, transfer the batter to another bowl through a strainer or colander.) The batter should be completely crumb-free and have the consistency between milk and heavy cream.
If possible, rest the batter in the fridge for 30-60 minutes (or more). If the batter separates, whisk again before frying palačinke, adding a pinch of water if necessary.
Heat a pan thoroughly over high heat. (However, if your stove runs hotter than most, you can cook them on medium, to medium-high heat. Adjust the temperature according to your stove.) Crunch up a paper towel, dip it in oil, and grease the pan lightly but thoroughly (watch your fingers!). (As you're using a small amount of oil on a very hot pan, there is no need to heat the oil further before adding the batter.)
Using a ladle (or a ½ cup measuring tool), pour the batter into the pan. Swirl the pan around (it may take a couple of swirls). The batter should swirl 'lazily' until it is distributed evenly over the surface. Cook the first side for 30 seconds to 1 minute, or until the edges start to brown and lift slightly. Flip with a spatula and cook the other side for 30 seconds more.
Palačinka Flipping Tip: If you're feeling confident, toss it in the air directly from the pan. Before flipping, ensure palačinka isn't stuck to the pan by gently shaking the pan from side to side.
Transfer cooked palačinka onto a plate, and cover it with a kitchen towel. For the best taste, wait until all are done before adding fillings. Stacking them allows them to soften and deepen flavor.
After one palačinka is done, coat the pan with oil again using the same paper towel method. While coating it, remove any crumbs that may have stayed from the previous crepe.
Repeat the cooking process until you finish the batter, or cook enough palačinka for one sitting. This amount of batter will give you about 17-18 crêpes.