You should not expect others to pay for your drinks.
John is invited by his coworkers to go to the bar after work, but he has no money left at the end of the month.
John wants to respond to the invitation.
John decides not to join their coworkers but agrees to join them next time.
John thinks that his manager who also joins them will pay the bill.
The coworkers offer to pay John's bill and insist that he should join them.
The coworkers pay their own bill after the activity and John feels embarrassed for not being able to pay for it himself.