Is there a certain environment where all cellular functions (or at least some) increase their rate?
There are optimal temperature, pressure and substrate concentration for each biochemical process. The optimal temperature and pressure for two or more (but not all) processes may overlap. So there is no SINGLE temperature or pressur where ALL of them will be at their maximum. Please note, by mentioning "cellular processes"  I meant all the biochemical(e.g glycolysis), physiological (cellular micro-transport) as well as physiochemical(transcription) processes. But we can try to provide substrates at reasonably high concentration ( keeping in mind negative feedback phenomena); we may reach the maximum achievable rate. All the above conditions follow bell-shaped curve; so I put the word 'resonably', as after the optimum condition is reached further increasing that condition will lead to decline in "speed" of reaction. We have to create an artificial enviornment using that substrate combination at proper concentration; as there is no such natural condition where that happens(cell always decrease one process while increasing another). 

But it may seem to be a paradox - does anabolic and catabolic reactions both will increase simultaneously! E.g glycogenesis and glycogenolysis at the same time......well, as I already said this is not a natural condition; we are forcing substrates of one reaction at "reasonable" concentration keeping in mind the 'opposite' (is it??) reaction. E.g glucose produces glycogen by glycogenesis and that new glycogen is used in glycogenolysis; so we have to consider the concentration of glucose only. Isn't that easy! well, not so soon. Doing this requires lot of ATP, of course we'll get some from the glucose breakdown, but the need is even higher. So we have to provide additional ATP. Then there are second messengers (cAMP, DAG, IP3 to name a few of them). We have to nutralize them all( they favours unidirectional process).....this is a very complicated thing(just for example, we are supplying ATP, so cAMP will be automatically produced; so we should select all the enzyme blockers of cAMP production). But then electrolyte concentration will be disturbed and we need to monitor &amp; regulate that also. 

Thus it is clear that such condition requires sofisticated laborarory instruments. 

N. B. 
1. I considered only a single cell while discussing this. 
2. The word "exhausted" was taken as progressive deterioration of cellular architecture, that leads to death.