Cut each bratwurst into bite-sized pieces, about an inch long, so you end up with roughly 24 pieces total. Heat the oil in a large skillet over medium-high heat and add the bratwurst pieces. Cook for about 10 minutes, turning occasionally, until they're browned on all sides and cooked through.
Remove the browned bratwurst pieces to a paper towel-lined plate to drain and cool slightly. While they cool, unroll the crescent dough sheet and press the seams together to form one solid rectangle. Slice it in half lengthwise, then into narrow strips so you have one strip per bratwurst piece.
Take one piece of bratwurst and wrap it snugly in a strip of crescent dough, letting the dough spiral around the sausage. Place each wrapped bite seam-side down on a parchment-lined baking sheet, spacing them a little apart so they bake evenly.
Whisk the egg and water together in a small bowl until fully combined. Lightly brush this mixture over each wrapped bite using your pastry brush, then sprinkle poppy seeds evenly across the top of every piece.
Slide the baking sheet into a preheated 375-degree oven and bake for 15 to 17 minutes, or until the dough turns a deep golden brown. Keep an eye on them near the end since ovens can vary quite a bit in how fast they brown.
While the bites bake, stir together the drained sauerkraut, mayonnaise, black pepper, and smoked paprika in a small bowl. Chill the sauce in the fridge until you're ready to serve, which helps all those flavors meld together nicely.