Bottle for containing liquid

A single-piece bottle comprising:

• a body portion, a cap-engaging portion and a neck;
• the cap-engaging portion defining an opening of the bottle and configured to engage with a bottle cap, said cap-engaging portion extending from an outer surface thereof;
• the neck comprising a top end and a bottom end, the top end of the neck being adjacent the cap-engaging portion closer to a bottle top end than a bottle bottom end;
• the neck further comprising an inner surface that defines a channel between the top end and the bottom end;
• the body portion extending from the bottom end of the neck and comprising a body inner surface that defines a liquid-containing space therein;
• and
• at least one inwardly-protruded spiral guide formed on the inner surface of the neck and configured to guide at least part of a liquid to spirally flow through the channel when discharging liquid from the liquid-containing space, wherein the at least one inwardly-protruded spiral guide generally spirally extends about a central axis of the bottle that passes through the channel and the liquid-containing space;
• wherein the at least one inwardly-protruded spiral guide extends circumferentially about the central axis about 180° or more.