In order to build authentic relationships with your coworkers, there are two things you have to be willing to do:
1. Invest your time.
2. Work hard and execute.
You have to invest time to get to know people, and unfortunately it doesn't usually happen between the hours of 9-5. Those people are "work friends" and they tend to not last if one of you ever leaves.
It's not authentic. It's based on whatever happened at work that day. Gossip, talking about a mean boss, etc. That doesn't last.
What is authentic? Sharing real feelings and stories. Sharing successes and failures. Getting to know others on a more personal level. Learning about someone's hobbies or interests, or learning about their family. Mixing relationships and going out socially with your "non-work friends" and your "work friends."
It all builds authenticity. It creates relationships that actually make work more rewarding.
Does it work all the time? Of course not. Not all people want new friends and not all people want to cross boundaries or take extra steps to invest in relationships.
People don't have to be friends with every person in the office; however, when you invite people into your home and you spend time beyond the work day with people, that's how you create authenticity.
When people don't open up and be honest, others see the wall they're putting up. I've seen people who keep a wall up and they say they are putting in time and working to develop relationships, however they don't let their guard down. They don't have honest conversations. They don't admit their vulnerabilities, and that's crucial to being authentic.
The other way to build strong relationships is through hard work and execution. If you aren't giving 100% of yourself at work, you can't expect to develop something meaningful with your coworkers.
Real work and execution results in a heck of a lot more than 40 hours a week. It's executing on your own work and helping out your teammates. It's the hours put in over the weekend to get a big project done. It's celebrating wins and learning from mistakes together.
People are naturally attracted to others who are willing to give up their time and execute on behalf of the team. Even if at first glance they didn't "like" you, when they see results and dedication, they will feel a connection to you on a deeper level.
At the end of the day, people want to be friends at work with people they know have as much on the line as they do, and work as hard as they do to help the team and company grow.
Hard work and execution builds respect, respect builds trust and trust is what relationships are built on.