Instructions:
1) Go into Restaurant City
2) Restaurant should be open, serving dishes to customers.
3) Download RC tool (link above) and extact everything to browser
4) Open RCCheat.exe
5) Select English or Spanish or Mandarin depending on your preferred language. Steps will be for English mode.
6) Select Browser (Firefox, maybe works with others too). Click Scan
7) Click Low-scan. Give it about 1-2minutes of scanning to get all buttons clickable.
Once scanning is done, select the cheats that you want! Take care when you use EXP cheat as excessive amount of EXP will become negative and you will not be able to rectify that!

Cheats includes:

Fast eat/customer/walk
Fast serve/cook/waiter
Infinite Stamina
EXP cheat
Speed hack
PAUSE quiz timing to search for answer
QUIZ to get all answers correct

Credits to pwnthis.net¡Enjoy!