Hello Xinx,

豆 dòu means a bean, 浆 jiāng means thick liquid, starch, which of course 豆浆 is, a thick liquid made from beans. 豆子 dòuzǐ however means a bean. 子 is often used in Chinese, it adds no meaning to the word but it makes the word longer so that it will be easier to understand, like
孩- 孩子 鞋- 鞋子 袜- 袜子 帽- 帽子
háizǐ child, xiézǐ shoes, wàzǐ socks, màozǐ hat.
Hat is a funny character, at the left the symbol 巾of a cloth, on the right on top the sun 日 and below the character of an eye 目, so a cloth to protect your eyes from the sun i.e. a hat!

Am I right Benny 我尊敬汉语老师?

Hope this will answer your question

万事如意

陆蓝克