To wish your friends who relate with the Hindu religion, you can wish him with something loving and craziest thoughts. You can describe something about his culture in that and wish him with Hindu birthday wishes.
List of Hindu birthday wishes
1. May Lord Shiva, give you strength and adherence to overcome any difficulties you face in your future endeavors! Happy Birthday.
2. I pray to Lord Vishnu to bless you with wisdom and knowledge. Wishing the best of health on your birthday.
3. Lord Hanuman shall give you the power to overcome any hurdles of life. Happy birthday.
4. Lord Ganesha may bless you with happiness on your special day and fill your day with surprises. Happy birthday.
5. May Lord Krishna enrich your life with all the blessings. Wishing you a Happy birthday.
6. Wish u a very happy birthday, may Lord Shiva bless u with lots of happiness & success in the world. Happy Birthday!
7. Lord Shiva walks each step of your journey with you as you walk through life. Happy Birthday.
8. As Lord Krishna said, May you prosper wherever you go and in whatever you do. Happy Birthday.
9. May Lord Ganesha bless you every day every way everywhere. Happy Birthday.
10.Happy Birthday! May Maa Durga continue to guide you on your path & bless you through your years.