Here you will learn how to obtain the yellowish water in Breathedge. It's one of the materials which you can craft. Upon collecting it, you will obtain its blueprint.
Yellowish water is a rarely used ingredient. You can craft it once you obtain its blueprint by using ice x4 on the processor. However, you won't have to do this often: the yellowish water is only used to craft the accelerator and its first upgrade.
To find the yellowish water, exit the first base and look to your right, towards the ice structures. You will find a toilet there, with yellowish water floating around it. Pick up one or more pieces. Contrary to what you may think, you can't obtain yellowish water by urinating in the toilet (or anywhere else).