Cap for container

A cap and container reduce carbonation loss in filling containers with carbonated beverages. The cap has a splashguard with a circular bottom connected by a conical transition to a smaller diameter, cylindrical ring portion. A circular dispersing disk is above the transition and connected to the cap, with a small radial gap between the disk's periphery and the splashguard. A fluid seal is interposed between the ring portion and an open top of the container. The dispersing disk directs a fluid stream outward against the splashguard where the fluid passes through the radial gap around the disk and flows downward in a laminar flow over the conical transition and ring portions. A lip on the bottom of the ring portion extends outward and downward to conduct the laminar flow onto the container sidewall, which is inclined at less than five degrees to maintain laminar flow along the sidewall when filling.