The buttocks sweat is a normal process. It’s an oily secretion that helps keep the skin moisturized and helps to regulate body temperature. When you exercise, your body needs more oil than usual to keep itself warm. The problem occurs when people allow their shirts or pants to ride up on their backsides allowing more of the sweat from their lower backbodies and glutes (buttocks) to get onto them while exercising so they feel like they need deodorant more often than normal. If this is happening to you, no matter how sweaty your shirt gets while working out, it shouldn’t be enough for you to want some deodorant afterwords because you don’t actually have any extra accumulation of sweat in your shirt or pants! You just got excited about what was happening at the gym and overcompensated by making yourself even hotter! So really, there’s nothing wrong with wearing a T-shirt during workouts if it makes you comfortable but wearing shorts will help prevent this issue altogether as well.
If your problem isn’t being able to control excessive sweating then I would recommend looking into using anti-perspirant/deodorants before heading off for a workout instead of trying not sweating throughout the workout which would only make things worse since now all of that facial moisture has nowhere else go.
Your best bet for preventing excessive sweating is learning how much humidity where ever you are going will be at during any given time period let alone