I suggest you choose PP (the bottom number is 5), 400ml and 500ml, which are quite cheap, non-toxic and odorless. They are sold in the supermarket. Silica gel resin is generally used as filler. If you choose it, better transparency means less filler. Dark color means more filler (of course, in order to save cost, the quality is not comparable)

Upstairs, it is said that there are all PP in 0.9 yuan. I saw it in Lekou. Mainly thin, the cost without cover is relatively low (including materials, simple molds, invisible advertisements made by merchants on cups).

There is also a PC speaker upstairs (PS: I don't mean upstairs). In June, many countries in the European Union issued relevant policies prohibiting the use of PCs as bottles. Although the performance of PC is very good, it is easy to decompose bisphenol A in hot water for a long time, which is harmful to brain cells and nerves, especially for students who use their brains. It is recommended not to use it.