Hey Sultan, how are you? Firstly, you should know that the correct sentence should be "I would like to trear you to a lunch". In this context, the word "treat (pronunced as "trët"- that is, like "tree" plus a "t" in the end- and often followed by "to") is used to indicate when a person wishes to provide another with something (as a treat); or when they wish to pay for another's entertainment, food, or drink. Below you shall find a set of useful examples: E.g.: "He treated the children to a trip to the zoo." E.g.: "I treated myself to a day in the country." E.g.: "You should treat him to a dinner - he is someone who commands respec!" Hope that helps!

It's not that formal, but it's commonly used among friends and acquaintances. It would be better to say, 'I would like to treat you to lunch.' It means you would like to pay for someone's meal (in Australia we say 'my shout' which means 'I will pay'). Treat is pronounced like 'tree' with a T on the end.