Hi, You both obviously do not like to carry weighty bottles around with you and so prefer sachets. But have you tried Kemdirect granular sachets which you can use top and bottom or only half a sachet at a time if no flush tank?
These are even more environmentally friendly as they contain no dye or smell and when used correctly there should be no chemical smell or odour from the toilet and just liquid when poured away.
If you visit www.kemdirect.nl you can read all about them and their inventor Hans, who is now on his own but used to be a biochemist for Thetford. All his products are more environmentally friendly and this was one of the reasons he went out on his own.
They too are also good value for money and very light to transport around.