Toxic water is a bit hard to get purposefully. The best source of drinking water is toxic water bottles, which are most easily found in water coolers. Fountain pens are also a decent source, as while they don't give much they are common and also have a chance to give precious ore. Dye is a decent source if you salvage a lot of food in your backpack, but is unpredictable to get.
|3 + 1||Toxic water bottle|
Research projects - random values
Toxic water bottle - open water tank and click this resource when you have at least 5 water of this type.