Some people are naturally blessed with odor-free armpits. Unfortunately, I am not one of them. However, I have here a quick guide to keeping those armpits smelling fresh however long you need them.
Products above are my current go to products.
First things first, these all have antiperspirant components. I've found that while deodorants smell cute, they don't last long once you start sweating if you naturally have the bacteria that turns your sweat into nuclear weapons. I've found that deodorants only work on me if I nuke my pits beforehand so it's inhospitable to life - and that leads to irritation and skin darkening so I've abandoned that route.
If you are the type of person that eschews antiperspirants, you had best be washing those pits frequently and reapplying deodorant as you go. Clean and sanitize your stick (or use a deodorant that's hard to contaminate) between each use, and ideally between armpits, as to avoid trapping bacteria there that will turn your deodorant into an actual source of stink.
But before applying product on your pits, you'd better clean them beforehand. Ideally, remove hair there since hair grabs on to things like dirt and sweat and oil. If you're not into that then just make sure to make sure its as clean as possible. I use regular soap but some prefer using astringents, acids and antibacterials. I've found that these more aggressive products work but can be too irritating so I've limited using those options only if I really do need that extra safety net. Pits should be completely dry unless you're using an alum stick as I do most days.
Just right after bathing, I use an antiperspirant. My daily driver is the Deonat Mineral Deodorant Stick since I can use it in the shower as a base before using another pit product. I love that it's cheap and lasts a crazy long time.
I also really like using the Fresh Sgt. At Arms (old reformulation) as a single use product on "light days" where it's not too hot or I'm not expecting to be out a lot. I've yet to try the newer formulation in newer packaging since I'm hesitant to pull the trigger because it looks like a very big price increase from before. It's now similar in price to the Snoe Beauty spray antiperspirant as well which I did like until the nozzle began to fail at the end of its life.
On 24 hours days I'll use a cream deodorant-antiperspirant combo like Dove Deodorant Dry Serum on top of my potassium alum Deonat base. On crazy sweaty days and 36 to 48 hours days I'll use a more heavy option like Secret Platinum Protection. I have a tried a few prescription strength products but I've found that they're very expensive and a bit overkill in terms of anti-perspirants strength and not very friendly to my skin health generally as they tend to stink. As I'm less likely to use them, they've all eventually expired. I think those with a more hyperhidrosis problem causing stink may benefit from prescription level products and I'm just not one of them.
Lastly, at the end of the day, I sniff my shirts (gross, but necessary) to see if any areas are stinky. I'll pretreat those spots with soap and/or colorsafe bleach to make sure I get rid of the stink that can be a source of smelly sauce even if my actual armpit skin smells fine. It also helps decrease the chances of unfavorable bacteria winning the war in the warzone that is the armpit.
I hope this helps someone out there.