Obvious solution
First off, shower just before heading to work. Use anti-perspirant. Carry a folded shirt and vest in your flight bag. Or two. Once the flight deck becomes dry, which it really does, change tops. Top of climb is a good plan. This works well for proper long-haul. No sweat.
If you have a turn-round in the heat, (ME folk particularly), then carry two sets of clean garments. It is hardly rocket science. Laundry is not costly. Comfort is important in this job. Change and feel dry.
I've flown alongside too many sweaty and smelly guys (not women).
Personal hygiene is important, but rarely discussed for pilots.