Well, I guess you can do it if super-organized.. I know some people who managed work, school, love, family (kids!) all at the same time..
It may not be for everyone, it's important to work on your health & energy & well-being too
maybe some time-management secrets can help? (GTD etc?)
& tips on studying, like browse through what you have to know for which exam, divide the stuff into topics and approximate amount of days needed to study this (older students from the same course can tell you! also they can tell you what individual professors expect etc. some stuff may be online too..)
use all techniques you can find.. there are books & articles on effective studying you can read & then most importantly - apply them
/like making notes, mind-maps, using colors, mnemotechnics.. - these were helpful to me, it depends if you are a visual learner or other, it's good to find out what you are & what's your easiest way of learning/
maybe you can find work where you can study in peace?
or take a break for exams & some time before exams indeed..?
at a time I was doing both work & studying & some extra courses I fell asleep on city bus, he he... then I was so tired I decided to just study for a while.. it really depends on the course a lot too, & the professors, the amount of time you have to be at the Uni, etc. maybe you can talk to some professors? maybe you don't have to be present at some courses so much? (just for the really important & necessary stuff?) depends on the profs & courses..
I'd say no to coffee.. never drank it much.. & sugar & alcohol & artificial pops.. & other unhealthy stuff.. make sure you get enough minerals & vitamins, ideally with natural food.. (some multivitamins can be problematic & don't have enough magnesium or such.. so you may be even more tired.. you can be more tired from soda drinks or sugar too, they rob you of good minerals & vitamins.. some of us learn these things a bit late.. )
Basically it's good to observe yourself & what you eat/do & how you feel, maybe keep a journal, & adjust according to how your body reacts..
Now I'm doing some online jobs.. Honestly, even if I am working inside my home, it's not that easy to manage my work and my school.. Since my course requires a lot of reading, sometimes I don't have time to read while at times, I miss my work deadlines.. I think it is best to stop working and concentrate with your studies.. Well, what makes it more difficult is that I also have a son to attend to..