This may include mere copy-pasting, minor text editing, data categorisation, translations and staff alike. You can work a few hours a day and earn some hundred bucks by the end of the month. Obviously, the total payout depends on how fast/good you are. Sign up to ClickWorker if you can tolerate handling some routine tasks in exchange for cash injections.
The best money-making move I’ve made so far at uni is to sign up to a few ‘extras’ agencies. You do literally nothing (just a bit of standing around on camera) and you get paid extremely well, often over £100 a day. You also get to creep on celebrities, which is always fun. If I had to choose between that and working in a busy pub, I know which one I’d go for.