Many tank cars do have baffles as even a full car is filled to no more than 80 of rated fluid
capacity to allow for expansion. Tank cars are often purpose built for a specific commodity type so design depends on intended commodity group. This is why railroads opted out of tank car ownership as they are so specific in their use that they spend large amounts of time sitting around as traffic is often seasonal. Even with baffles, when switching a loaded car with a liquid load you still feel the sloshing back and forth in the locomotive. Things like propane, ammonia, natural gas, chlorine, argon, etc. are shipped in a gas state (sometimes partly gas state) in a tank car designed for it. Propane (LPG) and ammonia can be shipped in the same car type, but only after the car has been completely purged of the prior commodity and as the process is rather costly, it is not often done. Cars loaded with a liquid commodity --- you can see the fluid level on a frosty morning, or when the car is loaded at a ship out point where it was say -10F
and it travels to a warm area the outside of the car will be frosty to the level of the liquid. Argon cars do not have domes, but rather a box on the underbelly and argon cars often will vent a white vapor out the top relief valve if the car is handled roughly for an extended period. Some tank cars have heating coils for commodities like: road tar, roofing tar, heavy raw crude oil etc. as the commodity has to be heated to flow properly. Asphalt is normally shipped hot in insulated tanks (that have heating coils as well) and as long as
the car gets where it's going in the required time frame can be unloaded without reheating.
Tank cars are complicated critters.