The best way to wear a tube top without your bra showing is to wear a bra that doesn't have straps. The best bra styles for this are a strapless bra, a bandeau bra, or a sticky bra.
A strapless bra with sturdy foam cups, a thick underwire, and wide side and back wings can be a supportive option for anyone looking to hide their bra straps beneath a tube top.
Bandeau bras feature a strapless, tube-like design that offers light support and coverage. They're perfect for pairing with off-the-shoulder or strapless tops and dresses. Bandeau bras work best for smaller busts that don't require extensive lift or shaping.
Sticky bras stick directly to the skin, providing light support without straps or a back band. Boob tape is another example of an adhesive bra option. These bras are excellent for clothing that has thin or no straps or an open or low back.