B737 MAX 8 Flight Attendant reported excessively warm cabin temperatures during several flights resulted in passenger and crew illness.

Narrative

Upon decent we noticed the cabin temp was warmer than usual. We were delayed for a failed APU and was told we would have it MEL and take care of it in ZZZ. We landed in ZZZ and it was very warm deplaning and was told that the Maintenance team would look at it while deplaning. The next thing I knew we were boarding. I called lead and asked what they said about the APU she said they MEL the unit and we are going to fly. After they opened the doors in the 90 degree heat we had an oven with unsafe temps for boarding and for take off. During boarding we had several people that were over heated and two needed sick bags after take off. With a full flight I had called lead before the door closed and told her that it was sweltering in the back - my guess was it was easy in the 90's in the back and mid cabin. I called a total of 4 times before we left and asked lead to tell the captain we have elderly and kids back here. With a full flight and body heat and tarmac temps in the 100's. I didn't understand why we were flying or why we boarded with it so hot in the cabin. I was then told it should be ok once up in the air. Fast forward 20 min it's still warmer than it should be for comfort. We then had three people get sick and the temps were super warm in the mid cabin and nowhere to move people. We were getting ice packs and water to people the entire flights to ZZZ -then ZZZ - ZZZ1. Then back to ZZZ -We land and it's summer in ZZZ1 and we went through the same issues all the way back to ZZZ. We then had another delay due to no gate space. Then another delay due to in op jet bridge total of 60 min delay without AC on a very hot tarmac. We then had to clean the plane and we were picking up sick bags like every other row. I picked up 6 in the back of the cabin and there was a mess in the bathroom as well. This is beyond not ok. This is unsafe for crew and passengers. We should have had Maintenance check the temp in the back after I called. I was completely soaked from sweat upon takeoff. And the knowing we had to fly in a cabin that was too warm for 2.5 hours and then back from ZZZ1 was discouraging. It was so warm on take off from ZZZ1 I felt lightheaded and tired of sweating the entire trip. It made it hard to do our job. I would like feedback on why it was ok to fly that day with no APU the cabin never cooled off. It made it very hard on us because we had to play nurse to a dozen pax during the flight. Also our ice was gone by service due to the heat so we had no relief even with ice on the ZZZ1 trip due to getting ice packs and the heat.