Token sinks are useful for countering holding stations; while holding stations can store more tokens than any token sink could absorb, the per-turn transfer limits only slightly favour the holding stations. By passing a stack over a token sink, almost all the excess tokens are absorbed and the otherwise overwhelming effects of a token cascade can be mitigated.
For most practical purposes, tokens absorbed by a token sink are lost for good. Even where some tokens can be retrieved, this usually costs more than the value of the tokens in question.
The Fronsky diagram symbol for a token sink containing retrievable tokens (a cache) is a solid underlined triangle with vertex pointing downwards. An empty token sink is marked by a hollow triangle with vertex pointing downward (no underscore). However, as token sinks of varying sizes are implicit to most stations they are not generally marked.