Undershirt of some sort. Sweating through a shirt out in public is rather unattractive looking.
How about an A-shirt (aka wife-beater)?
I never quite understood that, honestly, because it seems like it leaves the sweatiest parts -- the underarms -- exposed directly to the shirt. I know a lot of guys wear them. Am I missing something?
You need one of the new "Microfiber" undershirts. Someone mentioned UnderArmor, but they are now made by many other companies, including Jockey.
I cannot tell you the difference microfiber makes in clothing worn next to the skin. The fibers literally "wick" perspiration away from the body, so the fabric that stays in contact with your skin remains dry. It absolutely DOES NOT get "soggy" like cotton t-shirts do. Microfiber t-shirts hang dry very easily, and are generally simple to launder, they last longer, and retain their shape much better than cotton t-shirts.
Buy one, try it out, and report back with your findings.
I wear those underneath my kevlar. Which gets a bit warm in our 98-degree, humid nights.
Well, that certainly makes complaining about being a little warm in my button-down shirt seem a little silly.
under armor - jockey are two of the big names. Most large department stores now carry at least a few microfiber t-shirts. I believe i've even seen them at target.
One problem is that these shirts were originally developed for athletes, and as such they often have logos or stripes that may show through white shirts. Jockey, u/a, and a few other companies are now making "no visible logo" shirts without them.
You may find "off brand" microfiber shirts - you just need to look at the label. Look for things with 90-95% polyester, and 5% lycra or similar.