There are many styles of Sleeveless tops. So you need to know the scoop…hint, avoid the scoop neck when wearing a sleeveless tops.
Sleeveless tops are best if the strap is wider, not thinner, like that of a spaghetti strap. Also wear these type tops with a higher neckline, no revealing back, in a dressier, sturdy fabric. Casual fabrics only make the look less formal.
Always avoid sleeveless tops in formal business settings unless worn with a jacket. Remember to keep your jacket sleeves hemmed just at the break of the wrist, no longer than a ¼ of an inch, no matter what fashion tells you.
Remember your customers, internally and externally. When working in or with conservative clients opt not to show any upper arms! A cap sleeve often helps with this issue.