Soda is a base, while oil is an acid. When these two substances come into contact, they will react to form soap and water. This soap can clog the engine's oil passages, which can lead to serious engine damage.
In addition, the water formed by this reaction can cause the engine to rust from the inside out.
If you accidentally spill soda into your engine, it's important to flush it out with clean water as soon as possible. You should also change the oil and filter to remove any residual soap.
Never attempt to start the engine if you've spilled soda into it, as this could cause further damage.