how do you overcome sleepiness while working in the office ?

Have a cup of coffee.

take a rest buddy. it can heal you

There's a line in "Three Men in a Boat" by Jerome K Jerome that introduces one of the "Three" as - "Harris sleeps at a bank from 10 to 3". In other words, sleeping on the job is nothing new!

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I drink cofee

go slepe now

Get a goodnight's sleep on the previous night. Get up and take a walk probably meet someone personally in the office instead of sending a mail. You could alternatively Chew gum..

Have some healthy snacks like nuts and tea

Yes, that is true,,,   everyone will feel sleepy if they are tired, and everyone needs a very adequate rest to get rid of tiredness,

Get more sleep at night, drink coffee or get up and walk around a little if you are allowed.