Indian here, so experienced with hot climate.

• Wear loose cotton clothes (long-sleeved if stepping out in the hot sun)
• Keep yourself hydrated.
• Avoid soft/ aerated drinks/ soda & coffee as they'll dehydrate you. Stick to cool water, ice chips, fresh lemonade made with water, fresh fruit juices, melons, spinach-cucumber-onion-tomato salads, yoghurt,
• Eat light.
• Stick to well-ventilated rooms with good air-circulation (fans help)
• Cold water showers to cool down
• Sweating is good. It'll cool you down. This is also why Indians eat spicy food and drink hot tea even in hottest summer. Get sweaty then take a quick cold-water rinse.
• If you have to step outside in the hot sun, umbrella, hats, caps etc are your friends.
• Wet towel on the back of the neck for a quick cool down.

ETA: When it gets so hot that we lose our appetite, then our go-to meal is to mix up cooled cooked rice with unsweetened yoghurt and a pinch of salt. its variously called yoghurt rice/ curd rice/ thayir saadam / dahi bhaath / dahi chaawal . This is an easy to make & easy to diges meal that is guaranteed to cool a person down.

thayir = dahi = curd = yoghurt
saada = bhaath = chaawal = cooked rice

Good luck.